LaTeX2e unofficial reference manual (October 2018)

Short Table of Contents

Table of Contents

LaTeX2e: An unofficial reference manual

This document is an unofficial reference manual (version of October 2018) for LaTeX2e, a document preparation system.

1 About this document

This is an unofficial reference manual for the LaTeX2e document preparation system, which is a macro package for the TeX typesetting program (see Overview).

This document’s home page is https://puszcza.gnu.org.ua/software/latexrefman. There you can get the sources, subscribe to the mailing list or read its archives, see other infrastructure, and get the current output in various formats. In particular, the output comes in two web formats. Probably the most convenient one, shown at http://latexref.xyz/, has pages for each topic and so is good for a quick lookup; see also the note there about easy-to-remember links. The other, shown at http://svn.gnu.org.ua/viewvc/latexrefman/trunk/latex2e.html?view=co, has all the information on single page.

In this document, we will mostly just use ‘LaTeX’ rather than ‘LaTeX2e’, since the previous version of LaTeX (2.09) was frozen decades ago.

LaTeX is currently maintained by a group of volunteers (http://latex-project.org). The official documentation written by the LaTeX project is available from their web site. This document is completely unofficial and has not been reviewed by the LaTeX maintainers. Do not send bug reports or anything else about this document to them. Instead, please send all comments to latexrefman@tug.org.

This document is a reference. There is a vast array of other sources of information about LaTeX, at all levels. Here are a few introductions.

http://ctan.org/pkg/latex-doc-ptr

Two pages of recommended references to LaTeX documentation.

http://ctan.org/pkg/first-latex-doc

Writing your first document, with a bit of both text and math.

http://ctan.org/pkg/usrguide

The guide for document authors that is maintained as part of LaTeX. Many other guides by many other people are also available, independent of LaTeX itself; one such is the next item:

http://ctan.org/pkg/lshort

A short introduction to LaTeX, translated to many languages.

http://tug.org/begin.html

Introduction to the TeX system, including LaTeX, with further references.

2 Overview of LaTeX

LaTeX is a system for typesetting documents. It was originally created by Leslie Lamport and is now maintained by a group of volunteers (http://latex-project.org). It is widely used, particularly for complex and technical documents, such as those involving mathematics.

A LaTeX user writes an input file containing text along with interspersed commands, for instance commands describing how the text should be formatted. It is implemented as a set of related commands that interface with Donald E. Knuth’s TeX typesetting program (the technical term is that LaTeX is a macro package for the TeX engine). The user produces the output document by giving that input file to the TeX engine.

The term LaTeX is also sometimes used to mean the language in which the document is marked up, that is, to mean the set of commands available to a LaTeX user.

The name LaTeX is short for “Lamport TeX”. It is pronounced LAH-teck or LAY-teck, or sometimes LAY-tecks. Inside a document, produce the logo with \LaTeX. Where use of the logo is not sensible, such as in plain text, write it as ‘LaTeX’.

2.1 Starting and ending

LaTeX files have a simple global structure, with a standard beginning and ending. This is a small example.

\documentclass{article}
\begin{document}
Hello, \LaTeX\ world.
\end{document}

Every LaTeX document has a \begin{document} line and an \end{document} line.

Here, the ‘article’ is the document class. It is implemented in a file article.cls. You can use any document class on your system. A few document classes are defined by LaTeX itself, and vast array of others are widely available. See Document classes.

You can include other LaTeX commands between the \documentclass and the \begin{document} commands. This area is called the preamble.

The \begin{document}, \end{document} pair defines an environment; the ‘document’ environment (and no others) is required in all LaTeX documents (see document). LaTeX make available to you many environments that are documented here (see Environments). Many more are available to you from external packages, most importantly those available at CTAN (see CTAN).

The following sections discuss how to produce PDF or other output from a LaTeX input file.

2.2 Output files

LaTeX produces a main output file and at least two auxiliary files. The main output file’s name ends in either .dvi or .pdf.

.dvi

If LaTeX is invoked with the system command latex then it produces a DeVice Independent file, with extension .dvi. You can view this file with a command such as xdvi, or convert it to a PostScript .ps file with dvips or to a Portable Document Format .pdf file with dvipdfmx. The contents of the file can be dumped in human-readable form with dvitype. A vast array of other DVI utility programs are available (http://mirror.ctan.org/dviware).

.pdf

If LaTeX is invoked via the system command pdflatex, among other commands (see TeX engines), then the main output is a Portable Document Format (PDF) file. Typically this is a self-contained file, with all fonts and images included.

LaTeX also produces at least two additional files.

.log

This transcript file contains summary information such as a list of loaded packages. It also includes diagnostic messages and perhaps additional information for any errors.

.aux

Auxiliary information is used by LaTeX for things such as cross references. For example, the first time that LaTeX finds a forward reference—a cross reference to something that has not yet appeared in the source—it will appear in the output as a doubled question mark ??. When the referred-to spot does eventually appear in the source then LaTeX writes its location information to this .aux file. On the next invocation, LaTeX reads the location information from this file and uses it to resolve the reference, replacing the double question mark with the remembered location.

LaTeX may produce yet more files, characterized by the filename ending. These include a .lof file that is used to make a list of figures, a .lot file used to make a list of tables, and a .toc file used to make a table of contents (see Table of contents etc.). A particular class may create others; the list is open-ended.

2.3 TeX engines

LaTeX is defined to be a set of commands that are run by a TeX implementation (see Overview). This section gives a terse overview of the main programs (see also Command line).

latex

pdflatex

In TeX Live (http://tug.org/texlive), if LaTeX is invoked via either the system command latex or pdflatex, then the pdfTeX engine is run (http://ctan.org/pkg/pdftex). When invoked as latex, the main output is a .dvi file; as pdflatex, the main output is a .pdf file.

pdfTeX incorporates the e-TeX extensions to Knuth’s original program (http://ctan.org/pkg/etex), including additional programming features and bi-directional typesetting, and has plenty of extensions of its own. e-TeX is available on its own as the system command etex, but this is plain TeX (and produces .dvi).

In other TeX distributions, latex may invoke e-TeX rather than pdfTeX. In any case, the e-TeX extensions can be assumed to be available in LaTeX.

lualatex

If LaTeX is invoked via the system command lualatex, the LuaTeX engine is run (http://ctan.org/pkg/luatex). This program allows code written in the scripting language Lua (http://luatex.org) to interact with TeX’s typesetting. LuaTeX handles UTF-8 Unicode input natively, can handle OpenType and TrueType fonts, and produces a .pdf file by default. There is also dvilualatex to produce a .dvi file, but this is rarely used.

xelatex

If LaTeX is invoked with the system command xelatex, the XeTeX engine is run (http://tug.org/xetex). Like LuaTeX, XeTeX natively supports UTF-8 Unicode and TrueType and OpenType fonts, though the implementation is completely different, mainly using external libraries instead of internal code. XeTeX produces a .pdf file as output; it does not support DVI output.

Internally, XeTeX creates an .xdv file, a variant of DVI, and translates that to PDF using the (x)dvipdfmx program, but this process is automatic. The .xdv file is only useful for debugging.

Other variants of LaTeX and TeX exist, e.g., to provide additional support for Japanese and other languages ([u]pTeX, http://ctan.org/pkg/ptex, http://ctan.org/pkg/uptex).

2.4 LaTeX command syntax

In the LaTeX input file, a command name starts with a backslash character, \. The name itself then consists of either (a) a string of letters or (b) a single non-letter.

LaTeX commands names are case sensitive so that \pagebreak differs from \Pagebreak (the latter is not a standard command). Most commands are lowercase, but in any event you must enter all commands in the same case as they are defined.

A command may be followed by zero, one, or more arguments. These arguments may be either required or optional. Required arguments are contained in curly braces, {...}. Optional arguments are contained in square brackets, [...]. Generally, but not universally, if the command accepts an optional argument, it comes first, before any required arguments.

Inside of an optional argument, to use the character close square bracket (]) hide it inside curly braces, as in \item[closing bracket {]}]. Similarly, if an optional argument comes last, with no required argument after it, then to make the first character of the following text be an open square bracket, hide it inside curly braces.

Some of LaTeX’s commands are a declaration. Such a command changes the value the meaning of some other command or parameter. For instance, the \mainmatter declaration changes the typesetting of page numbers from roman numerals to arabic (see \frontmatter & \mainmatter & \backmatter).

LaTeX has the convention that some commands have a * form that is related to the form without a *, such as \chapter and \chapter*. The exact difference in behavior varies from command to command.

This manual describes all accepted options and *-forms for the commands it covers (barring unintentional omissions, a.k.a. bugs).

2.5 Environment

Synopsis:

\begin{environment name}
  ...
\end{environment name}

An area of LaTeX source, inside of which there is a distinct behavior. For instance, for poetry in LaTeX put the lines between \begin{verse} and \end{verse}.

\begin{verse}
  There once was a man from Nantucket \\
  ...
\end{verse}

See Environments for a list of environments. Particularly notable is that every LaTeX document must have a document environment, a \begin{document} ... \end{document} pair.

The environment name at the beginning must exactly match that at the end. This includes the case where environment name ends in a star (*); both the \begin and \end texts must include the star.

Environments may have arguments, including optional arguments. This example produces a table. The first argument is optional (and causes the table to be aligned on its top row) while the second argument is required (it specifies the formatting of columns).

\begin{tabular}[t]{r|l}
  ... rows of table ...
\end{tabular}

2.6 CTAN: the Comprehensive TeX Archive Network

The Comprehensive TeX Archive Network, CTAN, is the TeX and LaTeX community’s repository of free material. It is a set of Internet sites around the world that offer material related to LaTeX for download. Visit CTAN on the web at https://ctan.org.

This material is organized into packages, discrete bundles that typically offer some coherent functionality and are maintained by one person or a small number of people. For instance, many publishers have a package that allows authors to format papers to that publisher’s specifications.

In addition to the massive holdings, the web site offers features such as search by name or by functionality.

CTAN is not a single site, but instead is a set of sites. One of the sites is the core. This site actively manages the material, for instance, by accepting uploads of new or updated packages. It is hosted by the German TeX group DANTE e.V. Other sites around the world help out by mirroring, that is, automatically syncing their collections with the core site and then in turn making their copies publicly available. This gives users close to their location better access and relieves the load on the core site. The list of mirrors is at https://ctan.org/mirrors.

3 Document classes

The document’s overall class is defined with this command, which is normally the first command in a LaTeX source file.

\documentclass[options]{class}

The following document class names are built into LaTeX. (Many other document classes are available as separate packages; see Overview.)

article

For a journal article, a presentation, and miscellaneous general use.

book

Full-length books, including chapters and possibly including front matter, such as a preface, and back matter, such as an appendix (see Front/back matter).

letter

Mail, optionally including mailing labels (see Letters).

report

For documents of length between an article and a book, such as technical reports or theses, which may contain several chapters.

slides

For slide presentations—rarely used today. In its place the beamer package is perhaps the most prevalent (see beamer template).

Standard options are described in the next section.

3.1 Document class options

You can specify global options or class options to the \documentclass command by enclosing them in square brackets. To specify more than one option, separate them with a comma.

\documentclass[option1,option2,...]{class}

Here is the list of the standard class options.

All of the standard classes except slides accept the following options for selecting the typeface size (default is 10pt):

10pt  11pt  12pt

All of the standard classes accept these options for selecting the paper size (these show height by width):

a4paper

210 by 297mm (about 8.25 by 11.75 inches)

a5paper

148 by 210mm (about 5.8 by 8.3 inches)

b5paper

176 by 250mm (about 6.9 by 9.8 inches)

executivepaper

7.25 by 10.5 inches

legalpaper

8.5 by 14 inches

letterpaper

8.5 by 11 inches (the default)

When using one of the engines pdfLaTeX, LuaLaTeX, or XeLaTeX (see TeX engines), options other than letterpaper set the print area but you must also set the physical paper size. One way to do that is to put \pdfpagewidth=\paperwidth and \pdfpageheight=\paperheight in your document’s preamble.

The geometry package provides flexible ways of setting the print area and physical page size.

Miscellaneous other options:

draft

final

Mark (draft) or do not mark (final) overfull boxes with a black box in the margin; default is final.

fleqn

Put displayed formulas flush left; default is centered.

landscape

Selects landscape format; default is portrait.

leqno

Put equation numbers on the left side of equations; default is the right side.

openbib

Use “open” bibliography format.

titlepage

notitlepage

Specifies whether there is a separate page for the title information and for the abstract also, if there is one. The default for the report class is titlepage, for the other classes it is notitlepage.

The following options are not available with the slides class.

onecolumn

twocolumn

Typeset in one or two columns; default is onecolumn.

oneside

twoside

Selects one- or two-sided layout; default is oneside, except that in the book class the default is twoside.

For one-sided printing, the text is centered on the page. For two-sided printing, the \evensidemargin (\oddsidemargin) parameter determines the distance on even (odd) numbered pages between the left side of the page and the text’s left margin, with \oddsidemargin being 40% of the difference between \paperwidth and \textwidth, and \evensidemargin is the remainder.

openright

openany

Determines if a chapter should start on a right-hand page; default is openright for book, and openany for report.

The slides class offers the option clock for printing the time at the bottom of each note.

3.2 Additional packages

Load a package pkg, with the package options given in the comma-separated list options, as here.

\usepackage[options]{pkg}.

To specify more than one package you can separate them with a comma, as in \usepackage{pkg1,pkg2,...}, or use multiple \usepackage commands.

Any options given in the \documentclass command that are unknown to the selected document class are passed on to the packages loaded with \usepackage.

3.3 Class and package construction

You can create new document classes and new packages. For instance, if your memos must satisfy some local requirements, such as a standard header for each page, then you could create a new class smcmemo.cls and begin your documents with \documentclass{smcmemo}.

What separates a package from a document class is that the commands in a package are useful across classes while those in a document class are specific to that class. Thus, a command to set page headers is for a package while a command to make the page headers say Memo from the SMC Math Department is for a class.

Inside of a class or package file you can use the at-sign @ as a character in command names without having to surround the code containing that command with \makeatletter and \makeatother. See \makeatletter & \makeatother. This allow you to create commands that users will not accidentally redefine. Another technique is to preface class- or package-specific commands with some string to prevent your class or package from interfering with others. For instance, the class smcmemo might have commands \smc@tolist, \smc@fromlist, etc.

3.3.1 Class and package structure

A class file or package file typically has four parts.

1. In the identification part, the file says that it is a LaTeX package or class and describes itself, using the \NeedsTeXFormat and \ProvidesClass or \ProvidesPackage commands.
2. The preliminary declarations part declares some commands and can also load other files. Usually these commands will be those needed for the code used in the next part. For example, an smcmemo class might be called with an option to read in a file with a list of people for the to-head, as \documentclass[mathto]{smcmemo}, and therefore needs to define a command \newcommand{\setto}[1]{\def\@tolist{#1}} used in that file.
3. In the handle options part the class or package declares and processes its options. Class options allow a user to start their document as \documentclass[option list]{class name}, to modify the behavior of the class. An example is when you declare \documentclass[11pt]{article} to set the default document font size.
4. Finally, in the more declarations part the class or package usually does most of its work: declaring new variables, commands and fonts, and loading other files.

Here is a starting class file, which should be saved as stub.cls where LaTeX can find it, for example in the same directory as the .tex file.

\NeedsTeXFormat{LaTeX2e}
\ProvidesClass{stub}[2017/07/06 stub to start building classes from]
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
\ProcessOptions\relax
\LoadClass{article}

It identifies itself, handles the class options via the default of passing them all to the article class, and then loads the article class to provide the basis for this class’s code.

For more, see the official guide for class and package writers, the Class Guide, at http://www.latex-project.org/help/documentation/clsguide.pdf (much of the descriptions here derive from this document), or the tutorial https://www.tug.org/TUGboat/tb26-3/tb84heff.pdf.

3.3.2 Class and package commands

These are the commands designed to help writers of classes or packages.

\AtBeginDvi{specials}

Save in a box register things that are written to the .dvi file at the beginning of the shipout of the first page of the document.

\AtEndOfClass{code}

\AtEndOfPackage{code}

Hook to insert code to be executed when LaTeX finishes processing the current class or package. You can use these hooks multiple times; the code will be executed in the order that you called it. See also \AtBeginDocument.

\CheckCommand{cmd}[num][default]{definition}

\CheckCommand*{cmd}[num][default]{definition}

Like \newcommand (see \newcommand & \renewcommand) but does not define cmd; instead it checks that the current definition of cmd is exactly as given by definition and is or is not long as expected. A long command is a command that accepts \par within an argument. The cmd command is expected to be long with the unstarred version of \CheckCommand. Raises an error when the check fails. This allows you to check before you start redefining cmd yourself that no other package has already redefined this command.

\ClassError{class name}{error text}{help text}

\PackageError{package name}{error text}{help text}

\ClassWarning{class name}{warning text}

\PackageWarning{package name}{warning text}

\ClassWarningNoLine{class name}{warning text}

\PackageWarningNoLine{package name}{warning text}

\ClassInfo{class name}{info text}

\PackageInfo{package name}{info text}

\ClassInfoNoLine{class name}{info text}

\PackageInfoNoLine{package name}{info text}

Produce an error message, or warning or informational messages.

For \ClassError and \PackageError the message is error text, followed by TeX’s ? error prompt. If the user then asks for help by typing h, they see the help text.

The four warning commands are similar except that they write warning text on the screen with no error prompt. The four info commands write info text only in the transcript file. The NoLine versions do not show the number of the line generating the message, while the other versions do show that number.

To format the messages, including the help text: use \protect to stop a command from expanding, get a line break with \MessageBreak, and get a space with \space when a space character does not allow it, like after a command. Note that LaTeX appends a period to the messages.

\CurrentOption

Expands to the name of the currently-being-processed option. Can only be used within the code argument of either \DeclareOption or \DeclareOption*.

\DeclareOption{option}{code}

\DeclareOption*{code}

Make an option available to a user to invoke in their \documentclass command. For example, the smcmemo class could have an option \documentclass[logo]{smcmemo} allowing users to put the institutional logo on the first page. The class file must contain \DeclareOption{logo}{code} (and later, \ProcessOptions).

If you request an option that has not been declared, by default this will produce a warning like Unused global option(s): [badoption]. Change this behaviour with the starred version \DeclareOption*{code}. For example, many classes extend an existing class, using a declaration such as \LoadClass{article}, and for passing extra options to the underlying class use code such as this.

\DeclareOption*{%
\PassOptionsToClass{\CurrentOption}{article}%
}

Another example is that the class smcmemo may allow users to keep lists of memo recipients in external files. Then the user could invoke \documentclass[math]{smcmemo} and it will read the file math.memo. This code handles the file if it exists and otherwise passes the option to the article class.

\DeclareOption*{\InputIfFileExists{\CurrentOption.memo}{}{%
    \PassOptionsToClass{\CurrentOption}{article}}}

\DeclareRobustCommand{cmd}[num][default]{definition}

\DeclareRobustCommand*{cmd}[num][default]{definition}

Like \newcommand and \newcommand* (see \newcommand & \renewcommand) but these declare a robust command, even if some code within the definition is fragile. (For a discussion of robust and fragile commands see \protect.) Use this command to define new robust commands or to redefine existing commands and make them robust. Unlike \newcommand these do not give an error if macro cmd already exists; instead, a log message is put into the transcript file if a command is redefined.

Commands defined this way are a bit less efficient than those defined using \newcommand so unless the command’s data is fragile and the command is used within a moving argument, use \newcommand.

The etoolbox package offers the commands \newrobustcmd, \newrobustcmd*, as well as the commands \renewrobustcmd, \renewrobustcmd*, and the commands \providerobustcmd, and \providerobustcmd*. These are similar to \newcommand, \newcommand*, \renewcommand, \renewcommand*, \providecommand, and \providecommand*, but define a robust cmd with two advantages as compared to \DeclareRobustCommand:

1. They use the low-level e-TeX protection mechanism rather than the higher level LaTeX \protect mechanism, so they do not incur the slight loss of performance mentioned above, and
2. They make the same distinction between \new…, \renew…, and \provide…, as the standard commands, so they do not just make a log message when you redefine cmd that already exists, in that case you need to use either \renew… or \provide… or you get an error.

\IfFileExists{file name}{true code}{false code}

\InputIfFileExists{file name}{true code}{false code}

Execute true code if LaTeX finds the file file name or false code otherwise. In the first case it executing true code and then inputs the file. Thus the command

\IfFileExists{img.pdf}{%
  \includegraphics{img.pdf}}{\typeout{!! img.pdf not found}

will include the graphic img.pdf if it is found and otherwise give a warning.

This command looks for the file in all search paths that LaTeX uses, not only in the current directory. To look only in the current directory do something like \IfFileExists{./filename}{true code}{false code}. If you ask for a filename without a .tex extension then LaTeX will first look for the file by appending the .tex; for more on how LaTeX handles file extensions see \input.

\LoadClass[options list]{class name}[release date]

\LoadClassWithOptions{class name}[release date]

Load a class, as with \documentclass[options list]{class name}[release info]. An example is \LoadClass[twoside]{article}.

The options list, if present, is a comma-separated list. The release date is optional. If present it must have the form YYYY/MM/DD.

If you request a release date and the date of the package installed on your system is earlier, then you get a warning on the screen and in the log like this.

You have requested, on input line 4, version `2038/01/19' of
document class article, but only version `2014/09/29 v1.4h
Standard LaTeX document class' is available.

The command version \LoadClassWithOptions uses the list of options for the current class. This means it ignores any options passed to it via \PassOptionsToClass. This is a convenience command that lets you build classes on existing ones, such as the standard article class, without having to track which options were passed.

\ExecuteOptions{options-list}

For each option option in the options-list, in order, this command executes the command \ds@option. If this command is not defined then that option is silently ignored.

It can be used to provide a default option list before \ProcessOptions. For example, if in a class file you want the default to be 11pt fonts then you could specify \ExecuteOptions{11pt}\ProcessOptions\relax.

\NeedsTeXFormat{format}[format date]

Specifies the format that this class must be run under. Often issued as the first line of a class file, and most often used as: \NeedsTeXFormat{LaTeX2e}. When a document using that class is processed, the format name given here must match the format that is actually being run (including that the format string is case sensitive). If it does not match then execution stops with an error like ‘This file needs format `LaTeX2e' but this is `xxx'.’

To specify a version of the format that you know to have certain features, include the optional format date on which those features were implemented. If present it must be in the form YYYY/MM/DD. If the format version installed on your system is earlier than format date then you get a warning like this.

You have requested release `2038/01/20' of LaTeX, but only
release `2016/02/01' is available.

\OptionNotUsed

Adds the current option to the list of unused options. Can only be used within the code argument of either \DeclareOption or \DeclareOption*.

\PassOptionsToClass{option list}{class name}

\PassOptionsToPackage{option list}{package name}

Adds the options in the comma-separated list option list to the options used by any future \RequirePackage or \usepackage command for package package name or the class class name.

The reason for these commands is: you may load a package any number of times with no options but if you want options then you may only supply them when you first load the package. Loading a package with options more than once will get you an error like Option clash for package foo. (LaTeX throws an error even if there is no conflict between the options.)

If your own code is bringing in a package twice then you can collapse that to once, for example replacing the two \RequirePackage[landscape]{geometry} and \RequirePackage[margins=1in]{geometry} with the single command \RequirePackage[landscape,margins=1in]{geometry}.

However, imagine that you are loading firstpkg and inside that package it loads secondpkg, and you need the second package to be loaded with option draft. Then before doing the first package you must queue up the options for the second package, like this.

\PassOptionsToPackage{draft}{secondpkg}
\RequirePackage{firstpkg}

(If firstpkg.sty loads an option in conflict with what you want then you may have to alter its source.)

These commands are useful for general users as well as class and package writers. For instance, suppose a user wants to load the graphicx package with the option draft and also wants to use a class foo that loads the graphicx package, but without that option. The user could start their LaTeX file with \PassOptionsToPackage{draft}{graphicx}\documentclass{foo}.

\ProcessOptions

\ProcessOptions*\@options

Execute the code for each option that the user has invoked. Include it in the class file as \ProcessOptions\relax (because of the existence of the starred command).

Options come in two types. Local options have been specified for this particular package in the options argument of \PassOptionsToPackage{options}, \usepackage[options], or \RequirePackage[options]. Global options are those given by the class user in \documentclass[options] (If an option is specified both locally and globally then it is local.)

When \ProcessOptions is called for a package pkg.sty, the following happens:

1. For each option option so far declared with \DeclareOption, it looks to see if that option is either a global or a local option for pkg. If so then it executes the declared code. This is done in the order in which these options were given in pkg.sty.
2. For each remaining local option, it executes the command \ds@option if it has been defined somewhere (other than by a \DeclareOption); otherwise, it executes the default option code given in \DeclareOption*. If no default option code has been declared then it gives an error message. This is done in the order in which these options were specified.

When \ProcessOptions is called for a class it works in the same way except that all options are local, and the default code for \DeclareOption* is \OptionNotUsed rather than an error.

The starred version \ProcessOptions* executes the options in the order specified in the calling commands, rather than in the order of declaration in the class or package. For a package this means that the global options are processed first.

\ProvidesClass{class name}[release date brief additional information]

\ProvidesClass{class name}[release date]

\ProvidesPackage{package name}[release date brief additional information]

\ProvidesPackage{package name}[release date]

Identifies the class or package, printing a message to the screen and the log file.

When you load a class or package, for example with \documentclass{smcmemo} or \usepackage{test}, LaTeX inputs a file. If the name of the file does not match the class or package name declared in it then you get a warning. Thus, if you invoke \documentclass{smcmemo}, and the file smcmemo.cls has the statement \ProvidesClass{xxx} then you get a warning like You have requested document class `smcmemo', but the document class provides 'xxx'. This warning does not prevent LaTeX from processing the rest of the class file normally.

If you include the optional argument then you must include a date, before any spaces, of the form YYYY/MM/DD. The rest of the optional argument is free-form, although it traditionally identifies the class, and is written to the screen during compilation and to the log file. Thus, if your file smcmemo.cls contains the line \ProvidesClass{smcmemo}[2008/06/01 v1.0 SMC memo class] and your document’s first line is \documentclass{smcmemo} then you will see Document Class: smcmemo 2008/06/01 v1.0 SMC memo class.

The date in the optional argument allows class and package users to ask to be warned if the version of the class or package is earlier than release date. For instance, a user could enter \documentclass{smcmemo}[2018/10/12] or \usepackage{foo}[[2017/07/07]] to require a class or package with certain features by specifying that it must be released no earlier than the given date. (Although, in practice package users only rarely include a date, and class users almost never do.)

\ProvidesFile{file name}[additional information]

Declare a file other than the main class and package files, such as configuration files or font definition files. Put this command in that file and you get in the log a string like File: test.config 2017/10/12 config file for test.cls for file name equal to ‘test.config’ and additional information equal to ‘2017/10/12 config file for test.cls’.

\RequirePackage[option list]{package name}[release date]

\RequirePackageWithOptions{package name}[release date]

Load a package, like the command \usepackage (see Additional packages). The LaTeX development team strongly recommends use of these commands over Plain TeX’s \input; see the Class Guide. An example is \RequirePackage[landscape,margin=1in]{geometry}.

The option list, if present, is a comma-separated list. The release date, if present, must have the form YYYY/MM/DD. If the release date of the package as installed on your system is earlier than release date then you get a warning like You have requested, on input line 9, version `2017/07/03' of package jhtest, but only version `2000/01/01' is available.

The \RequirePackageWithOptions version uses the list of options for the current class. This means it ignores any options passed to it via \PassOptionsToClass. This is a convenience command to allow easily building classes on existing ones without having to track which options were passed.

The difference between \usepackage and \RequirePackage is small. The \usepackage command is intended for the document file while \RequirePackage is intended for package and class files. Thus, using \usepackage before the \documentclass command causes LaTeX to give error like \usepackage before \documentclass, but you can use \RequirePackage there.

4 Fonts

Two important aspects of selecting a font are specifying a size and a style. The LaTeX commands for doing this are described here.

4.1 Font styles

The following type style commands are supported by LaTeX.

In the table below the listed commands, the \text... commands, is used with an argument, as in \textit{text}. This is the preferred form. But shown after it, in parenthesis, is the corresponding declaration form, which is sometimes useful. This form takes no arguments, as in {\itshape text}. The scope of the declaration form lasts until the next type style command or the end of the current group. In addition, each has an environment form such as \begin{itshape}...\end{itshape}.

These commands, in both the argument form and the declaration form, are cumulative; for instance you can get bold sans serif by saying either of \sffamily\bfseries or \bfseries\sffamily.

One advantage of these commands is that they automatically insert italic corrections if needed (see \/). Specifically, they insert the italic correction unless the following character is in the list \nocorrlist, which by default consists of a period and a comma. To suppress the automatic insertion of italic correction, use \nocorr at the start or end of the command argument, such as \textit{\nocorr text} or \textsc{text \nocorr}.

\textrm (\rmfamily)

Roman.

\textit (\itshape)

Italics.

\textmd (\mdseries)

Medium weight (default).

\textbf (\bfseries)

Boldface.

\textup (\upshape)

Upright (default).

\textsl (\slshape)

Slanted.

\textsf (\sffamily)

Sans serif.

\textsc (\scshape)

Small caps.

\texttt (\ttfamily)

Typewriter.

\textnormal (\normalfont)

Main document font.

Although it also changes fonts, the \emph{text} command is semantic, for text to be emphasized, and should not be used as a substitute for \textit. For example, \emph{start text \emph{middle text} end text} will result in the start text and end text in italics, but middle text will be in roman.

LaTeX also provides the following commands, which unconditionally switch to the given style, that is, are not cumulative. They are used as declarations: {\cmd...} instead of \cmd{...}.

(The unconditional commands below are an older version of font switching. The earlier commands are an improvement in most circumstances. But sometimes an unconditional font switch is precisely what you want.)

\bf

Switch to bold face.

\cal

Switch to calligraphic letters for math.

\it

Italics.

\rm

Roman.

\sc

Small caps.

\sf

Sans serif.

\sl

Slanted (oblique).

\tt

Typewriter (monospace, fixed-width).

The \em command is the unconditional version of \emph.

The following commands are for use in math mode. They are not cumulative, so \mathbf{\mathit{symbol}} does not create a boldface and italic symbol; instead, it will just be in italics. This is because typically math symbols need consistent typographic treatment, regardless of the surrounding environment.

\mathrm

Roman, for use in math mode.

\mathbf

Boldface, for use in math mode.

\mathsf

Sans serif, for use in math mode.

\mathtt

Typewriter, for use in math mode.

\mathit

(\mit)

Italics, for use in math mode.

\mathnormal

For use in math mode, e.g., inside another type style declaration.

\mathcal

Calligraphic letters, for use in math mode.

In addition, the command \mathversion{bold} can be used for switching to bold letters and symbols in formulas. \mathversion{normal} restores the default.

Finally, the command \oldstylenums{numerals} will typeset so-called “old-style” numerals, which have differing heights and depths (and sometimes widths) from the standard “lining” numerals, which all have the same height as uppercase letters. LaTeX’s default fonts support this, and will respect \textbf (but not other styles; there are no italic old-style numerals in Computer Modern). Many other fonts have old-style numerals also; sometimes the textcomp package must be loaded, and sometimes package options are provided to make them the default. FAQ entry: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=osf.

4.2 Font sizes

The following standard type size commands are supported by LaTeX. The table shows the command name and the corresponding actual font size used (in points) with the ‘10pt’, ‘11pt’, and ‘12pt’ document size options, respectively (see Document class options).

The commands are listed here in declaration forms. You use them by declaring them, as with this example.

\begin{quotation} \small
  The Tao that can be named is not the eternal Tao.
\end{quotation}

The scope of the \small lasts until the end of the quotation environment. It would also end at the next type style command or the end of the current group, so you could enclose it in extra curly braces {\small We are here, we are here, we are here!}. You can instead use the environment form of these commands; for instance, \begin{tiny}...\end{tiny}.

4.3 Low-level font commands

These commands are primarily intended for writers of macros and packages. The commands listed here are only a subset of the available ones.

\fontencoding{encoding}

Select the font encoding, the encoding of the output font. There are a large number of valid encodings. The most common are OT1, Knuth’s original encoding for Computer Modern (the default), and T1, also known as the Cork encoding, which has support for the accented characters used by the most widespread European languages (German, French, Italian, Polish and others), which allows TeX to hyphenate words containing accented letters. For more, see https://ctan.org/pkg/encguide.

\fontfamily{family}

Select the font family. The web page http://www.tug.dk/FontCatalogue/ provides one way to browse through many of the fonts easily used with LaTeX. Here are examples of some common families.

pag	Avant Garde
fvs	Bitstream Vera Sans
pbk	Bookman
bch	Charter
ccr	Computer Concrete
cmr	Computer Modern
cmss	Computer Modern Sans Serif
cmtt	Computer Modern Typewriter
pcr	Courier
phv	Helvetica
fi4	Inconsolata
lmr	Latin Modern
lmss	Latin Modern Sans
lmtt	Latin Modern Typewriter
pnc	New Century Schoolbook
ppl	Palatino
ptm	Times
uncl	Uncial
put	Utopia
pzc	Zapf Chancery

\fontseries{series}

Select the font series. A series combines a weight and a width. Typically, a font supports only a few of the possible combinations. Some common combined series values include:

m	Medium (normal)
b	Bold
c	Condensed
bc	Bold condensed
bx	Bold extended

The possible values for weight, individually, are:

ul	Ultra light
el	Extra light
l	Light
sl	Semi light
m	Medium (normal)
sb	Semi bold
b	Bold
eb	Extra bold
ub	Ultra bold

The possible values for width, individually, are (the meaning and relationship of these terms varies with individual typefaces):

uc	Ultra condensed
ec	Extra condensed
c	Condensed
sc	Semi condensed
m	Medium
sx	Semi expanded
x	Expanded
ex	Extra expanded
ux	Ultra expanded

When forming the series string from the weight and width, drop the m that stands for medium weight or medium width, unless both weight and width are m, in which case use just one (‘m’).

\fontshape{shape}

Select font shape. Valid shapes are:

n	Upright (normal)
it	Italic
sl	Slanted (oblique)
sc	Small caps
ui	Upright italics
ol	Outline

The two last shapes are not available for most font families, and small caps are often missing as well.

\fontsize{size}{skip}

Set the font size and the line spacing. The unit of both parameters defaults to points (pt). The line spacing is the nominal vertical space between lines, baseline to baseline. It is stored in the parameter \baselineskip. The default \baselineskip for the Computer Modern typeface is 1.2 times the \fontsize. Changing \baselineskip directly is inadvisable since its value is reset every time a size change happens; see \baselinestretch, next.

\baselinestretch

LaTeX multiplies the line spacing by the value of the \baselinestretch parameter; the default factor is 1. A change takes effect when \selectfont (see below) is called. You can make a line skip change happen for the entire document, for instance doubling it, by doing \renewcommand{\baselinestretch}{2.0} in the preamble.

However, the best way to double-space a document is to use the setspace package. In addition to offering a number of spacing options, this package keeps the line spacing single-spaced in places where that is typically desirable, such as footnotes and figure captions. See the package documentation.

\linespread{factor}

Equivalent to \renewcommand{\baselinestretch}{factor}, and therefore must be followed by \selectfont to have any effect. Best specified in the preamble, or use the setspace package, as just described.

\selectfont

The effects of the font commands described above do not happen until \selectfont is called, as in \fontfamily{familyname}\selectfont. It is often useful to put this in a macro:
\newcommand*{\myfont}{\fontfamily{familyname}\selectfont}
(see \newcommand & \renewcommand).

\usefont{enc}{family}{series}{shape}

The same as invoking \fontencoding, \fontfamily, \fontseries and \fontshape with the given parameters, followed by \selectfont. For example:

\usefont{ot1}{cmr}{m}{n}

5 Layout

Commands for controlling the general page layout.

5.1 \onecolumn

Synopsis:

\onecolumn

Start a new page and produce single-column output. If the document is given the class option onecolumn then this is the default behavior (see Document class options). This command is fragile (see \protect).

5.2 \twocolumn

Synopses:

\twocolumn
\twocolumn[prelim one column text]

Start a new page and produce two-column output. If the document is given the class option twocolumn then this is the default (see Document class options). This command is fragile (see \protect).

If the optional prelim one column text argument is present, it is typeset in one-column mode before the two-column typesetting starts.

These parameters control typesetting in two-column output:

\columnsep

The distance between columns. The default is 35pt. Change it with a command such as \setlength{\columnsep}{40pt} You must change it before the two column environment starts; in the preamble is a good place.

\columnseprule

The width of the rule between columns. The rule appears halfway between the two columns. The default is 0pt, meaning that there is no rule. Change it with a command such as \setlength{\columnseprule}{0.4pt}, before the two-column environment starts.

\columnwidth

The width of a single column. In one-column mode this is equal to \textwidth. In two-column mode by default LaTeX sets the width of each of the two columns to be half of \textwidth minus \columnsep.

In a two-column document, the starred environments table* and figure* are two columns wide, whereas the unstarred environments table and figure take up only one column (see figure and see table). LaTeX places starred floats at the top of a page. The following parameters control float behavior of two-column output.

\dbltopfraction

The maximum fraction at the top of a two-column page that may be occupied by two-column wide floats. The default is 0.7, meaning that the height of a table* or figure* environment must not exceed 0.7\textheight . If the height of your starred float environment exceeds this then you can take one of the following actions to prevent it from floating all the way to the back of the document:

• Use the [tp] location specifier to tell LaTeX to try to put the bulky float on a page by itself, as well as at the top of a page.
• Use the [t!] location specifier to override the effect of \dbltopfraction for this particular float.
• Increase the value of \dbltopfraction to a suitably large number, to avoid going to float pages so soon.

You can redefine it, as with \renewcommand{\dbltopfraction}{0.9}.

\dblfloatpagefraction

For a float page of two-column wide floats, this is the minimum fraction that must be occupied by floats, limiting the amount of blank space. LaTeX’s default is 0.5. Change it with \renewcommand.

\dblfloatsep

On a float page of two-column wide floats, this length is the distance between floats, at both the top and bottom of the page. The default is 12pt plus2pt minus2pt for a document set at 10pt or 11pt, and 14pt plus2pt minus4pt for a document set at 12pt.

\dbltextfloatsep

This length is the distance between a multi-column float at the top or bottom of a page and the main text. The default is 20pt plus2pt minus4pt.

\dbltopnumber

On a float page of two-column wide floats, this counter gives the maximum number of floats allowed at the top of the page. The LaTeX default is 2.

This example uses \twocolumn’s optional argument of to create a title that spans the two-column article:

\documentclass[twocolumn]{article}
\newcommand{\authormark}[1]{\textsuperscript{#1}}
\begin{document}
\twocolumn[{% inside this optional argument goes one-column text
  \centering
  \LARGE The Title \\[1.5em]
  \large Author One\authormark{1},
         Author Two\authormark{2},
         Author Three\authormark{1} \\[1em]
  \normalsize
  \begin{tabular}{p{.2\textwidth}@{\hspace{2em}}p{.2\textwidth}}
    \authormark{1}Department one  &\authormark{2}Department two \\ 
     School one                   &School two 
  \end{tabular}\\[3em] % space below title part
  }]

Two column text here.

5.3 \flushbottom

Make all pages in the documents after this declaration have the same height, by stretching the vertical space where necessary to fill out the page. This is most often used when making two-sided documents since the differences in facing pages can be glaring.

If TeX cannot satisfactorily stretch the vertical space in a page then you get a message like ‘Underfull \vbox (badness 10000) has occurred while \output is active’. If you get that, one option is to change to \raggedbottom (see \raggedbottom). Alternatively, you can adjust the textheight to make compatible pages, or you can add some vertical stretch glue between lines or between paragraphs, as in \setlength{\parskip}{0ex plus0.1ex}. Your last option is to, in a final editing stage, adjust the height of individual pages (see \enlargethispage).

The \flushbottom state is the default only if you select the twoside document class option (see Document class options).

5.4 \raggedbottom

Make all later pages the natural height of the material on that page; no rubber vertical lengths will be stretched. Thus, in a two-sided document the facing pages may be different heights. This command can go at any point in the document body. See \flushbottom.

This is the default unless you select the twoside document class option (see Document class options).

5.5 Page layout parameters

\columnsep

\columnseprule

\columnwidth

The distance between the two columns, the width of a rule between the columns, and the width of the columns, when the document class option twocolumn is in effect (see Document class options). See \twocolumn.

\headheight

Height of the box that contains the running head. The default in the article, report, and book classes is ‘12pt’, at all type sizes.

\headsep

Vertical distance between the bottom of the header line and the top of the main text. The default in the article and report classes is ‘25pt’. In the book class the default is: if the document is set at 10pt then it is ‘0.25in’, and at 11pt and 12pt it is ‘0.275in’.

\footskip

Distance from the baseline of the last line of text to the baseline of the page footer. The default in the article and report classes is ‘30pt’. In the book class the default is: when the type size is 10pt the default is ‘0.35in’, while at 11pt it is ‘0.38in’, and at 12pt it is ‘30pt’.

\linewidth

Width of the current line, decreased for each nested list (see list). That is, the nominal value for \linewidth is to equal \textwidth but for each nested list the \linewidth is decreased by the sum of that list’s \leftmargin and \rightmargin (see itemize).

\marginparpush

\marginsep

\marginparwidth

The minimum vertical space between two marginal notes, the horizontal space between the text body and the marginal notes, and the horizontal width of the notes.

Normally marginal notes appear on the outside of the page, but the declaration \reversemarginpar changes that (and \normalmarginpar changes it back).

The defaults for \marginparpush in both book and article classes are: ‘7pt’ if the document is set at 12pt, and ‘5pt’ if the document is set at 11pt or 10pt.

For \marginsep, in article class the default is ‘10pt’ except if the document is set at 10pt and in two-column mode where the default is ‘11pt’.

For \marginsep in book class the default is ‘10pt’ in two-column mode and ‘7pt’ in one-column mode.

For \marginparwidth in both book and article classes, in two-column mode the default is 60% of \paperwidth - \textwidth, while in one-column mode it is 50% of that distance.

\oddsidemargin

\evensidemargin

The \oddsidemargin is the extra distance between the left side of the page and the text’s left margin, on odd-numbered pages when the document class option twoside is chosen and on all pages when oneside is in effect. When twoside is in effect, on even-numbered pages the extra distance on the left is evensidemargin.

LaTeX’s default is that \oddsidemargin is 40% of the difference between \paperwidth and \textwidth, and \evensidemargin is the remainder.

\paperheight

The height of the paper, as distinct from the height of the print area. Normally set with a document class option, as in \documentclass[a4paper]{article} (see Document class options).

\paperwidth

The width of the paper, as distinct from the width of the print area. Normally set with a document class option, as in \documentclass[a4paper]{article} (see Document class options).

\textheight

The normal vertical height of the page body. If the document is set at a nominal type size of 10pt then for an article or report the default is ‘43\baselineskip’, while for a book it is ‘41\baselineskip’. At a type size of 11pt the default is ‘38\baselineskip’ for all document classes. At 12pt it is ‘36\baselineskip’ for all classes.

\textwidth

The full horizontal width of the entire page body. For an article or report document, the default is ‘345pt’ when the chosen type size is 10pt, the default is ‘360pt’ at 11pt, and it is ‘390pt’ at 12pt. For a book document, the default is ‘4.5in’ at a type size of 10pt, and ‘5in’ at 11pt or 12pt.

In multi-column output, \textwidth remains the width of the entire page body, while \columnwidth is the width of one column (see \twocolumn).

In lists (see list), \textwidth remains the width of the entire page body (and \columnwidth the width of the entire column), while \linewidth may decrease for nested lists.

Inside a minipage (see minipage) or \parbox (see \parbox), all the width-related parameters are set to the specified width, and revert to their normal values at the end of the minipage or \parbox.

\hsize

This entry is included for completeness: \hsize is the TeX primitive parameter used when text is broken into lines. It should not be used in normal LaTeX documents.

\topmargin

Space between the top of the TeX page (one inch from the top of the paper, by default) and the top of the header. The value is computed based on many other parameters: \paperheight - 2in - \headheight - \headsep - \textheight - \footskip, and then divided by two.

\topskip

Minimum distance between the top of the page body and the baseline of the first line of text. For the standard classes, the default is the same as the font size, e.g., ‘10pt’ at a type size of 10pt.

5.6 Floats

Some typographic elements, such as figures and tables, cannot be broken across pages. They must be typeset outside of the normal flow of text, for instance floating to the top of a later page.

LaTeX can have a number of different classes of floating material. The default is the two classes, figure (see figure) and table (see table), but you can create a new class with the package float.

Within any one float class LaTeX always respects the order, so that the first figure in a document source must be typeset before the second figure. However, LaTeX may mix the classes, so it can happen that while the first table appears in the source before the first figure, it appears in the output after it.

The placement of floats is subject to parameters, given below, that limit the number of floats that can appear at the top of a page, and the bottom, etc. If so many floats are queued that the limits prevent them all from fitting on a page then LaTeX places what it can and defers the rest to the next page. In this way, floats may end up being typeset far from their place in the source. In particular, a float that is big may migrate to the end of the document. In which event, because all floats in a class must appear in sequential order, every following float in that class also appears at the end.

In addition to changing the parameters, for each float you can tweak where the float placement algorithm tries to place it by using its placement argument. The possible values are a sequence of the letters below. The default for both figure and table, in both article and book classes, is tbp.

t

(Top)—at the top of a text page.

b

(Bottom)—at the bottom of a text page. (However, b is not allowed for full-width floats (figure*) with double-column output. To ameliorate this, use the stfloats or dblfloatfix package, but see the discussion at caveats in the FAQ: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=2colfloat.

h

(Here)—at the position in the text where the figure environment appears. However, h is not allowed by itself; t is automatically added.

To absolutely force a float to appear “here”, you can \usepackage{float} and use the H specifier which it defines. For further discussion, see the FAQ entry at http://www.tex.ac.uk/cgi-bin/texfaq2html?label=figurehere.

p

(Page of floats)—on a separate float page, which is a page containing no text, only floats.

!

Used in addition to one of the above; for this float only, LaTeX ignores the restrictions on both the number of floats that can appear and the relative amounts of float and non-float text on the page. The ! specifier does not mean “put the float here”; see above.

Note: the order in which letters appear in the placement argument does not change the order in which LaTeX tries to place the float; for instance, btp has the same effect as tbp. All that placement does is that if a letter is not present then the algorithm does not try that location. Thus, LaTeX’s default of tbp is to try every location except placing the float where it occurs in the source.

To prevent LaTeX from moving floats to the end of the document or a chapter you can use a \clearpage command to start a new page and insert all pending floats. If a pagebreak is undesirable then you can use the afterpage package and issue \afterpage{\clearpage}. This will wait until the current page is finished and then flush all outstanding floats.

LaTeX can typeset a float before where it appears in the source (although on the same output page) if there is a t specifier in the placement parameter. If this is not desired, and deleting the t is not acceptable as it keeps the float from being placed at the top of the next page, then you can prevent it by either using the flafter package or using the command \suppressfloats[t], which causes floats for the top position on this page to moved to the next page.

Parameters relating to fractions of pages occupied by float and non-float text (change them with \renewcommand{parameter}{decimal between 0 and 1}):

\bottomfraction

The maximum fraction of the page allowed to be occupied by floats at the bottom; default ‘.3’.

\floatpagefraction

The minimum fraction of a float page that must be occupied by floats; default ‘.5’.

\textfraction

Minimum fraction of a page that must be text; if floats take up too much space to preserve this much text, floats will be moved to a different page. The default is ‘.2’.

\topfraction

Maximum fraction at the top of a page that may be occupied before floats; default ‘.7’.

Parameters relating to vertical space around floats (change them with a command of the form \setlength{parameter}{length expression}):

\floatsep

Space between floats at the top or bottom of a page; default ‘12pt plus2pt minus2pt’.

\intextsep

Space above and below a float in the middle of the main text; default ‘12pt plus2pt minus2pt’ for 10 point and 11 point documents, and ‘14pt plus4pt minus4pt’ for 12 point documents.

\textfloatsep

Space between the last (first) float at the top (bottom) of a page; default ‘20pt plus2pt minus4pt’.

Counters relating to the number of floats on a page (change them with a command of the form \setcounter{ctrname}{natural number}):

bottomnumber

Maximum number of floats that can appear at the bottom of a text page; default 1.

dbltopnumber

Maximum number of full-sized floats that can appear at the top of a two-column page; default 2.

topnumber

Maximum number of floats that can appear at the top of a text page; default 2.

totalnumber

Maximum number of floats that can appear on a text page; default 3.

The principal TeX FAQ entry relating to floats http://www.tex.ac.uk/cgi-bin/texfaq2html?label=floats contains suggestions for relaxing LaTeX’s default parameters to reduce the problem of floats being pushed to the end. A full explanation of the float placement algorithm is in Frank Mittelbach’s article “How to influence the position of float environments like figure and table in LaTeX?” (http://latex-project.org/papers/tb111mitt-float.pdf).

6 Sectioning

Structure your text into divisions: parts, chapters, sections, etc. All sectioning commands have the same form, one of:

sectioning-command{title}
sectioning-command*{title}
sectioning-command[toc-title]{title}

For instance, declare the start of a subsection as with \subsection{Motivation}.

The table has each sectioning-command in LaTeX. All are available in all of LaTeX’s standard document classes book, report, and article, except that \chapter is not available in article.

All these commands have a *-form that prints title as usual but is not numbered and does not make an entry in the table of contents. An example of using this is for an appendix in an article . The input \appendix\section{Appendix} gives the output ‘A Appendix’ (see \appendix). You can lose the numbering ‘A’ by instead entering \section*{Appendix} (articles often omit a table of contents and have simple page headers so the other differences from the \section command may not matter).

The section title title provides the heading in the main text, but it may also appear in the table of contents and in the running head or foot (see Page styles). You may not want the same text in these places as in the main text. All of these commands have an optional argument toc-title for these other places.

The level number in the table above determines which sectional units are numbered, and which appear in the table of contents. If the sectioning command’s level is less than or equal to the value of the counter secnumdepth then the titles for this sectioning command will be numbered (see Sectioning/secnumdepth). And, if level is less than or equal to the value of the counter tocdepth then the table of contents will have an entry for this sectioning unit (see Sectioning/tocdepth).

LaTeX expects that before you have a \subsection you will have a \section and, in a book, that before a \section you will have a \chapter. Otherwise you can get a something like a subsection numbered ‘3.0.1’.

Two counters relate to the appearance of sectioning commands.

secnumdepth

Controls which sectioning commands are numbered. Suppress numbering of sectioning at any depth greater than level \setcounter{secnumdepth}{level} (see \setcounter). See the above table for the level numbers. For instance, if the secnumdepth is 1 in an article then a \section{Introduction} command will produce output like ‘1 Introduction’ while \subsection{Discussion} will produce output like ‘Discussion’, without the number. LaTeX’s default secnumdepth is 3 in article class and  2 in the book and report classes.

tocdepth

Controls which sectioning units are listed in the table of contents. The setting \setcounter{tocdepth}{level} makes the sectioning units at level be the smallest ones listed (see \setcounter). See the above table for the level numbers. For instance, if tocdepth is 1 then the table of contents will list sections but not subsections. LaTeX’s default secnumdepth is 3 in article class and  2 in the book and report classes.

6.1 \part

Synopsis, one of:

\part{title}
\part*{title}
\part[toc-title]{title}

Start a document part. The standard LaTeX classes book, report, and article, all have this command.

This produces a document part, in a book.

\part{VOLUME I \\
       PERSONAL MEMOIRS OF  U.\ S.\ GRANT}
\chapter{ANCESTRY--BIRTH--BOYHOOD.}
My family is American, and has been for generations,
in all its branches, direct and collateral.

In each standard class the \part command outputs a part number such as ‘Part I’, alone on its line, in boldface, and in large type. Then LaTeX outputs title, also alone on its line, in bold and in even larger type. In class book, the LaTeX default puts each part alone on its own page. If the book is two-sided then LaTeX will skip a page if needed to have the new part on an odd-numbered page. In report it is again alone on a page, but LaTeX won’t force it onto an odd-numbered page. In an article LaTeX does not put it on a fresh page, but instead outputs the part number and part title onto the main document page.

The * form shows title but it does not show the part number, does not increment the part counter, and produces no table of contents entry.

The optional argument toc-title will appear as the part title in the table of contents (see Table of contents etc.) and in running headers (see Page styles). If it is not present then title will be there. This example puts a line break in title but leaves out the break in the table of contents.

\part[Up from the bottom; my life]{Up from the bottom\\ my life}

For determining which sectional units are numbered and which appear in the table of contents, the level number of a part is -1 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

In the class article, if a paragraph immediately follows the part title then it is not indented. To get an indent you can use the package indentfirst.

One package to change the behavior of \part is titlesec. See its documentation on CTAN.

6.2 \chapter

Synopsis, one of:

\chapter{title}
\chapter*{title}
\chapter[toc-title]{title}

Start a chapter. The standard LaTeX classes book and report have this command but article does not.

This produces a chapter.

\chapter{Loomings}
Call me Ishmael.
Some years ago---never mind how long precisely---having little or no
money in my purse, and nothing particular to interest me on shore, I
thought I would sail about a little and see the watery part of
the world.

The LaTeX default starts each chapter on a fresh page, an odd-numbered page if the document is two-sided. It produces a chapter number such as ‘Chapter 1’ in large boldface type (the size is \huge). It then puts title on a fresh line, in boldface type that is still larger (size \Huge). It also increments the chapter counter, adds an entry to the table of contents (see Table of contents etc.), and sets the running header information (see Page styles).

The * form shows title on a fresh line, in boldface. But it does not show the chapter number, does not increment the chapter counter, produces no table of contents entry, and does not affect the running header. (If you use the page style headings in a two-sided document then the header will be from the prior chapter.) This example illustrates.

\chapter*{Preamble}

The optional argument toc-title will appear as the chapter title in the table of contents (see Table of contents etc.) and in running headers (see Page styles). If it is not present then title will be there. This shows the full name in the chapter title,

\chapter[Weyl]{Hermann Klaus Hugo (Peter) Weyl (1885--1955)}

but only ‘Weyl’ on the contents page. This puts a line break in the title but that doesn’t work well with running headers so it omits the break in the contents

\chapter[Given it all\\ my story]{Given it all\\ my story}

For determining which sectional units are numbered and which appear in the table of contents, the level number of a chapter is 0 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the chapter title is not indented, as is a standard typographical practice. To get an indent use the package indentfirst.

You can change what is shown for the chapter number. To change it to something like ‘Lecture 1’, put in the preamble either \renewcommand{\chaptername}{Lecture} or this (see \makeatletter & \makeatother).

\makeatletter
\renewcommand{\@chapapp}{Lecture}
\makeatother

To make this change because of the primary language for the document, see the package babel.

In a two-sided document LaTeX puts a chapter on odd-numbered page, if necessary leaving an even-numbered page that is blank except for any running headers. To make that page completely blank, see \clearpage & \cleardoublepage.

To change the behavior of the \chapter command, you can copy its definition from the LaTeX format file and make adjustments. But there are also many packages on CTAN that address this. One is titlesec. See its documentation, but the example below gives a sense of what it can do.

\usepackage{titlesec}   % in preamble
\titleformat{\chapter}
  {\Huge\bfseries}  % format of title
  {}                % label, such as 1.2 for a subsection
  {0pt}             % length of separation between label and title
  {}                % before-code hook

This omits the chapter number ‘Chapter 1’ from the page but unlike \chapter* it keeps the chapter in the table of contents and the running headers.

6.3 \section

Synopsis, one of:

\section{title}
\section*{title}
\section[toc-title]{title}

Start a section. The standard LaTeX classes article, book, and report all have this command.

This produces a section.

In this Part we tend to be more interested in the function,
in the input-output behavior,
than in the details of implementing that behavior.

\section{Turing machines}
Despite this desire to downplay implementation,
we follow the approach of A~Turing that the
first step toward defining the set of computable functions
is to reflect on the details of what mechanisms can do.

For the standard LaTeX classes book and report the default output is like ‘1.2 title’ (for chapter 1, section 2), alone on its line and flush left, in boldface and a larger type (the type size is \Large). The same holds in article except that there are no chapters in that class so it looks like ‘2 title’.

The * form shows title. But it does not show the section number, does not increment the section counter, produces no table of contents entry, and does not affect the running header. (If you use the page style headings in a two-sided document then the header will be from the prior section.)

The optional argument toc-title will appear as the section title in the table of contents (see Table of contents etc.) and in running headers (see Page styles). If it is not present then title will be there. This shows the full name in the title of the section,

\section[Elizabeth~II]{Elizabeth the Second,
  by the Grace of God of the United Kingdom,
  Canada and Her other Realms and Territories Queen,
  Head of the Commonwealth, Defender of the Faith.}

but only ‘Elizabeth II’ on the contents page and in the headers. This has a line break in title but that does not work with headers so it is omitted from the contents and headers.

\section[Truth is, I cheated; my life story]{Truth is,
  I cheated\\my life story}

For determining which sectional units are numbered and which appear in the table of contents, the level number of a section is 1 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the section title is not indented, as is a standard typographical practice. One way to get an indent is to use the package indentfirst.

In general, to change the behavior of the \section command, there are a number of options. One is the \@startsection command (see \@startsection). There are also many packages on CTAN that address this, including titlesec. See the documentation but the example below gives a sense of what they can do.

\usepackage{titlesec}   % in preamble
\titleformat{\section}
  {\normalfont\Large\bfseries}  % format of title
  {\makebox[1pc][r]{\thesection\hspace{1pc}}} % label
  {0pt}                   % length of separation between label and title
  {}                      % before-code hook
\titlespacing*{\section}
  {-1pc}{18pt}{10pt}[10pc]

That puts the section number in the margin.

6.4 \subsection

Synopsis, one of:

\subsection{title}
\subsection*{title}
\subsection[toc-title]{title}

Start a subsection. The standard LaTeX classes article, book, and report all have this command.

This produces a subsection.

We will show that there are more functions than Turing machines and that
therefore some functions have no associated machine.

\subsection{Cardinality} We will begin with two paradoxes that
dramatize the challenge to our intuition posed by comparing the sizes of
infinite sets.

For the standard LaTeX classes book and report the default output is like ‘1.2.3 title’ (for chapter 1, section 2, subsection 3), alone on its line and flush left, in boldface and a larger type (the type size is \large). The same holds in article except that there are no chapters in that class so it looks like ‘2.3 title’.

The * form shows title. But it does not show the section number, does not increment the section counter, and produces no table of contents entry.

The optional argument toc-title will appear as the section title in the table of contents (see Table of contents etc.). If it is not present then title will be there. This shows the full name in the title of the section,

\subsection[$\alpha,\beta,\gamma$ paper]{\textit{The Origin of
  Chemical Elements} by R.A.~Alpher, H.~Bethe, and G.~Gamow}

but only ‘α,β,γ paper’ on the contents page.

For determining which sectional units are numbered and which appear in the table of contents, the level number of a subsection is 2 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the subsection title is not indented, as is a standard typographical practice. One way to get an indent is to use the package indentfirst.

There are a number of ways to change the behavior of the \subsection command. One is the \@startsection command (see \@startsection). There are also many packages on CTAN that address this, including titlesec. See the documentation but the example below gives a sense of what they can do.

\usepackage{titlesec}   % in preamble
\titleformat{\subsection}[runin]
  {\normalfont\normalsize\bfseries}  % format of the title
  {\thesubsection}                   % label
  {0.6em}                            % space between label and title
  {}                                 % before-code hook

That puts the subsection number and title in the first line of text.

6.5 \subsubsection, \paragraph, \subparagraph

Synopsis, one of:

\subsubsection{title}
\subsubsection*{title}
\subsubsection[toc-title]{title}

or one of:

\paragraph{title}
\paragraph*{title}
\paragraph[toc-title]{title}

or one of:

\subparagraph{title}
\subparagraph*{title}
\subparagraph[toc-title]{title}

Start a subsubsection, paragraph, or subparagraph. The standard LaTeX classes article, book, and report all have these commands, although they are not commonly used.

This produces a subsubsection.

\subsubsection{Piston ring compressors: structural performance}
Provide exterior/interior wall cladding assemblies
capable of withstanding the effects of load and stresses from 
consumer-grade gasoline engine piston rings.

The default output of each of the three does not change over the standard LaTeX classes article, book, and report. For \subsubsection the title is alone on its line, in boldface and normal size type. For \paragraph the title is inline with the text, not indented, in boldface and normal size type. For \subparagraph the title is inline with the text, with a paragraph indent, in boldface and normal size type (Because an article has no chapters its subsubsections are numbered and so it looks like ‘1.2.3 title’, for section 1, subsection 2, and subsubsection 3. The other two divisions are not numbered.)

The * form shows title. But it does not increment the associated counter and produces no table of contents entry (and does not show the number for \subsubsection).

The optional argument toc-title will appear as the division title in the table of contents (see Table of contents etc.). If it is not present then title will be there.

For determining which sectional units are numbered and which appear in the table of contents, the level number of a subsubsection is 3, of a paragraph is 4, and of a subparagraph is 5 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the subsubsection title is not indented, as is a standard typographical practice. One way to get an indent is to use the package indentfirst.

There are a number of ways to change the behavior of the these commands. One is the \@startsection command (see \@startsection). There are also many packages on CTAN that address this, including titlesec. See the documentation on CTAN.

6.6 \appendix

Synopsis:

\appendix

This does not directly produce any output. But in a book or report it declares that subsequent \chapter commands start an appendix. In an article it does the same, for \section commands. It also resets the chapter and section counters to 0 in a book or report, and in an article resets the section and subsection counters.

In this book

\chapter{One}  ...
\chapter{Two}  ...
 ...
\appendix
\chapter{Three}  ...
\chapter{Four}  ...

the first two will generate output numbered ‘Chapter 1’ and ‘Chapter 2’. After the \appendix the numbering will be ‘Appendix A’ and ‘Appendix B’. See Larger book template for another example.

The appendix package adds the command \appendixpage to put a separate ‘Appendices’ in the document body before the first appendix, and the command \addappheadtotoc to do the same in the table of contents. You can reset the name ‘Appendix’ with a command like \renewcommand{\appendixname}{Specification}, as well as a number of other features. See the documentation on CTAN.

6.7 \frontmatter, \mainmatter, \backmatter

Synopsis, one of:

\frontmatter
\mainmatter
\backmatter

Format a book class document differently according to which part of the document is being produced. All three commands are optional.

Traditionally, a book’s front matter contains such things as the title page, an abstract, a table of contents, a preface, a list of notations, a list of figures, and a list of tables. (Some of these front matter pages, such as the title page, are traditionally not numbered.) The back matter may contain such things as a glossary, notes, a bibliography, and an index.

The \frontmatter declaration makes the pages numbered in lowercase roman, and makes chapters not numbered, although each chapter’s title appears in the table of contents; if you use other sectioning commands here, use the *-version (see Sectioning). The \mainmatter changes the behavior back to the expected version, and resets the page number. The \backmatter leaves the page numbering alone but switches the chapters back to being not numbered. See Larger book template for an example using the three.

6.8 \@startsection

Synopsis:

\@startsection{name}{level}{indent}{beforeskip}{afterskip}{style}

Used to help redefine the behavior of commands that start sectioning divisions such as \section or \subsection.

Note that the titlesec package makes manipulation of sectioning easier. Further, while most requirements for sectioning commands can be satisfied with \@startsection, some cannot. For instance, in the standard LaTeX book and report classes the commands \chapter and \report are not constructed in this way. To make such a command you may want to use the \secdef command.

Technically, \@startsection has the form

\@startsection{name}
  {level}
  {indent}
  {beforeskip}
  {afterskip}
  {style}*[toctitle]{title}

so that issuing

\renewcommand{\section}{\@startsection{name}
  {level}
  {indent}
  {beforeskip}
  {afterskip}
  {style}}

redefines \section to have the form \section*[toctitle]{title} (here too, the star * is optional). See Sectioning. This implies that when you write a command like \renewcommand{section}{...}, the \@startsection{...} must come last in the definition. See the examples below.

name

Name of the counter used to number the sectioning header. This counter must be defined separately. Most commonly this is either section, subsection, or paragraph. Although in those cases the counter name is the same as the sectioning command itself, you don’t have to use the same name.

Then \thename displays the title number and \namemark is for the page headers. See the third example below.

level

An integer giving the depth of the sectioning command. See Sectioning for the list of standard level numbers.

If level is less than or equal to the value of the counter secnumdepth then titles for this sectioning command will be numbered (see Sectioning/secnumdepth). For instance, if secnumdepth is 1 in an article then the command \section{Introduction} will produce output like “1 Introduction” while \subsection{Discussion} will produce output like “Discussion”, without the number prefix.

If level is less than or equal to the value of the counter tocdepth then the table of contents will have an entry for this sectioning unit (see Sectioning/tocdepth). For instance, in an article, if tocdepth is 1 then the table of contents will list sections but not subsections.

indent

A length giving the indentation of all of the title lines with respect to the left margin. To have the title flush with the margin use 0pt. A negative indentation such as -\parindent will move the title into the left margin.

beforeskip

The absolute value of this length is the amount of vertical space that is inserted before this sectioning unit’s title. This space will be discarded if the sectioning unit happens to start at the top of a fresh page. If this number is negative then the first paragraph following the header is not indented, if it is non-negative then the first paragraph is indented. (Note that the negative of 1pt plus 2pt minus 3pt is -1pt plus -2pt minus -3pt.)

For example, if beforeskip is -3.5ex plus -1ex minus -0.2ex then to start the new sectioning unit, LaTeX will add about 3.5 times the height of a letter x in vertical space, and the first paragraph in the section will not be indented. Using a rubber length, with plus and minus, is good practice here since it gives LaTeX more flexibility in making up the page (see Lengths).

The full accounting of the vertical space between the baseline of the line prior to this sectioning unit’s header and the baseline of the header is that it is the sum of the \parskip of the text font, the \baselineskip of the title font, and the absolute value of the beforeskip. This space is typically rubber so it may stretch or shrink. (If the sectioning unit starts on a fresh page so that the vertical space is discarded then the baseline of the header text will be where LaTeX would put the baseline of the first text line on that page.)

afterskip

This is a length. If afterskip is non-negative then this is the vertical space inserted after the sectioning unit’s title header. If it is negative then the title header becomes a run-in header, so that it becomes part of the next paragraph. In this case the absolute value of the length gives the horizontal space between the end of the title and the beginning of the following paragraph. (Note that the negative of 1pt plus 2pt minus 3pt is -1pt plus -2pt minus -3pt.)

As with beforeskip, using a rubber length, with plus and minus components, is good practice here since it gives LaTeX more flexibility in putting together the page.

If afterskip is non-negative then the full accounting of the vertical space between the baseline of the sectioning unit’s header and the baseline of the first line of the following paragraph is that it is the sum of the \parskip of the title font, the \baselineskip of the text font, and the value of after. That space is typically rubber so it may stretch or shrink. (Note that because the sign of afterskip changes the sectioning unit header’s from standalone to run-in, you cannot use a negative afterskip to cancel part of the \parskip.)

style

Controls the styling of the title. See the examples below. Typical commands to use here are \centering, \raggedright, \normalfont, \hrule, or \newpage. The last command in style may be one that takes one argument, such as \MakeUppercase or \fbox that takes one argument. The section title will be supplied as the argument to this command. For instance, setting style to \bfseries\MakeUppercase would produce titles that are bold and uppercase.

These are LaTeX’s defaults for the first three sectioning units that are defined with \@startsection, for the article, book, and report classes. For section, the level is 1, the indent is 0pt, the beforeskip is -3.5ex plus -1ex minus -0.2ex, the afterskip is 2.3ex plus 0.2ex, and the style is \normalfont\Large\bfseries. For subsection, the level is 2, the indent is 0pt, the beforeskip is -3.25ex plus -1ex minus -0.2ex, the afterskip is 1.5ex plus 0.2ex, and the style is \normalfont\large\bfseries. For subsubsection, the level is 3, the indent is 0pt, the beforeskip is -3.25ex plus -1ex minus -0.2ex, the afterskip is 1.5ex plus 0.2ex, and the style is \normalfont\normalsize\bfseries.

Here are examples. They go either in a package or class file or in the preamble of a LaTeX document. If you put them in the preamble they must go between a \makeatletter command and a \makeatother. (Probably the error message You can't use `\spacefactor' in vertical mode. means that you forgot this.) See \makeatletter & \makeatother.

This will put section titles in large boldface type, centered. It says \renewcommand because LaTeX’s standard classes have already defined a \section. For the same reason it does not define a section counter, or the commands \thesection and \l@section.

\renewcommand\section{%
  \@startsection{section}% name
    {1}% level
    {0pt}% indent
    {-3.5ex plus -1ex minus -.2ex}% beforeskip
    {2.3ex plus.2ex}% afterskip
    {\centering\normalfont\Large\bfseries}% style
  }

This will put subsection titles in small caps type, inline with the paragraph.

\renewcommand\subsection{%
  \@startsection{subsection}%  name
    {2}% level
    {0em}% indent
    {-1ex plus 0.1ex minus -0.05ex}% beforeskip
    {-1em plus 0.2em}% afterskip
    {\scshape}% style
  }

The prior examples redefined existing sectional unit title commands. This defines a new one, illustrating the needed counter and macros to display that counter.

\setcounter{secnumdepth}{6}% show counters this far down
\newcounter{subsubparagraph}[subparagraph]% counter for numbering
\renewcommand{\thesubsubparagraph}%               how to display 
  {\thesubparagraph.\@arabic\c@subsubparagraph}%  numbering
\newcommand{\subsubparagraph}{\@startsection
                         {subsubparagraph}%
                         {6}%
                         {0em}%
                         {\baselineskip}%
                         {0.5\baselineskip}%
                         {\normalfont\normalsize}}
\newcommand*\l@subsubparagraph{\@dottedtocline{6}{10em}{5em}}% for toc
\newcommand{\subsubparagraphmark}[1]{}% for page headers

7 Cross references

We often want something like ‘See Theorem~31’. But by-hand typing the 31 is poor practice. Instead you should write a label such as \label{eq:GreensThm} and then reference it, as with See equation~\ref{eq:GreensThm}. LaTeX will automatically work out the number, put it into the output, and will change that number later if needed.

We will see this with Theorem~\ref{th:GreensThm}. % forward reference
...
\begin{theorem} \label{th:GreensThm}
  ...
\end{theorem}
...
See Theorem~\ref{th:GreensThm} on page~\pageref{th:GreensThm}.

LaTeX tracks cross reference information in a file having the extension .aux and with the same base name as the file containing the \label. So if \label is in calculus.tex then the information is in calculus.aux. LaTeX puts the information in that file every time it runs across a \label.

The behavior described in the prior paragraph results in a quirk that happens when your document has a forward reference, a \ref that appears before the associated \label. If this is the first time that you are compiling the document then you will get ‘LaTeX Warning: Label(s) may have changed. Rerun to get cross references right’ and in the output the forward reference will appear as two question marks ‘??’, in boldface. A similar thing happens if you change some things so the references changes; you get the same warning and the output contains the old reference information. In both cases, resolve this by compiling the document a second time.

The cleveref package enhances LaTeX’s cross referencing features. You can arrange that if you enter \begin{thm}\label{th:Nerode}...\end{thm} then \cref{th:Nerode} will output ‘Theorem 3.21’, without you having to enter the “Theorem.”

7.1 \label

Synopsis:

\label{key}

Assign a reference number to key. In ordinary text \label{key} assigns to key the number of the current sectional unit. Inside an environment with numbering, such as a table or theorem environment, \label{key} assigns to key the number of that environment. Retrieve the assigned number with the \ref{key} command (see \ref).

A key name can consist of any sequence of letters, digits, or common punctuation characters. Upper and lowercase letters are distinguished, as usual.

A common convention is to use labels consisting of a prefix and a suffix separated by a colon or period. Thus, \label{fig:Post} is a label for a figure with a portrait of Emil Post. This helps to avoid accidentally creating two labels with the same name, and makes your source more readable. Some commonly-used prefixes:

ch

for chapters

sec

subsec

for lower-level sectioning commands

fig

for figures

tab

for tables

eq

for equations

In the auxiliary file the reference information is kept as the text of a command of the form \newlabel{label}{{currentlabel}{pagenumber}}. Here currentlabel is the current value of the macro \@currentlabel that is usually updated whenever you call \refstepcounter{counter}.

Below, the key sec:test will get the number of the current section and the key fig:test will get the number of the figure. (Incidentally, put labels after captions in figures and tables.)

\section{section name}
\label{sec:test}
This is Section~\ref{sec:test}.
\begin{figure}
  ...
  \caption{caption text}
  \label{fig:test}
\end{figure}
See Figure~\ref{fig:test}.

7.2 \pageref

Synopsis:

\pageref{key}

Produce the page number of the place in the text where the corresponding \label{key} command appears.

If there is no \label{key} then you get something like ‘LaTeX Warning: Reference `th:GrensThm' on page 1 undefined on input line 11.’

Below, the \label{eq:main} is used both for the formula number and for the page number. (Note that the two references are forward references so this document would need to be compiled twice to resolve those.)

The main result is formula~\ref{eq:main} on page~\pageref{eq:main}.
  ...
\begin{equation} \label{eq:main}
   \mathbf{P}=\mathbf{NP}
\end{equation}

7.3 \ref

Synopsis:

\ref{key}

Produces the number of the sectional unit, equation, footnote, figure, …, of the corresponding \label command (see \label). It does not produce any text, such as the word ‘Section’ or ‘Figure’, just the bare number itself.

If there is no \label{key} then you get something like ‘LaTeX Warning: Reference `th:GrensThm' on page 1 undefined on input line 11.’

In this example the \ref{popular} produces ‘2’. Note that it is a forward reference since it comes before \label{popular} so this document would have to be compiled twice.

The most widely-used format is item number~\ref{popular}.
\begin{enumerate}
\item Plain \TeX
\item \label{popular} \LaTeX
\item Con\TeX t
\end{enumerate}

The cleveref package includes text such as ‘Theorem’ in the reference. See the documentation on CTAN.

8 Environments

LaTeX provides many environments for delimiting certain behavior. An environment begins with \begin and ends with \end, like this:

\begin{environment-name}
  ...
\end{environment-name}

The environment-name at the beginning must exactly match that at the end. For instance, the input \begin{table*}...\end{table} will cause an error like: ‘! LaTeX Error: \begin{table*} on input line 5 ended by \end{table}.’

Environments are executed within a group.

8.1 abstract

Synopsis:

\begin{abstract}
...
\end{abstract}

Produce an abstract, possibly of multiple paragraphs. This environment is only defined in the article and report document classes (see Document classes).

Using the example below in the article class produces a displayed paragraph. Document class option titlepage causes the abstract to be on a separate page (see Document class options); this is the default only in the report class.

\begin{abstract}
  We compare all known accounts of the proposal made by Porter Alexander 
  to Robert E Lee at the Appomattox Court House that the army continue
  in a guerrilla war, which Lee refused.
\end{abstract}

The next example produces a one column abstract in a two column document (for a more flexible solution, use the package abstract).

\documentclass[twocolumn]{article}
  ...
\begin{document}
\title{Babe Ruth as Cultural Progenitor: a Atavistic Approach}
\author{Smith \\ Jones \\ Robinson\thanks{Railroad tracking grant.}}
\twocolumn[
  \begin{@twocolumnfalse}
     \maketitle
     \begin{abstract}
       Ruth was not just the Sultan of Swat, he was the entire swat
       team.   
     \end{abstract}
   \end{@twocolumnfalse}
   ]
{   % by-hand insert a footnote at page bottom
 \renewcommand{\thefootnote}{\fnsymbol{footnote}}
 \footnotetext[1]{Thanks for all the fish.}
}

8.2 array

Synopsis:

\begin{array}{cols}
  column 1 entry &column 2 entry ... &column n entry \\
  ...
\end{array}

or:

\begin{array}[pos]{cols}
  column 1 entry &column 2 entry ... &column n entry \\
  ...
\end{array}

Produce a mathematical array. This environment can only be used in math mode, and normally appears within a displayed mathematics environment such as equation (see equation). Inside of each row the column entries are separated by an ampersand, (&). Rows are terminated with double-backslashes (see \\).

This example shows a three by three array.

\begin{equation*}
  \chi(x) =
  \left|              % vertical bar fence
    \begin{array}{ccc}
      x-a  &-b  &-c  \\
      -d   &x-e &-f  \\
      -g   &-h  &x-i
    \end{array}
 \right|
\end{equation*}

The required argument cols describes the number of columns, their alignment, and the formatting of the intercolumn regions. For instance, \begin{array}{rcl}...\end{array} gives three columns: the first flush right, the second centered, and the third flush left. See tabular for the complete description of cols and of the other common features of the two environments, including the optional pos argument.

There are two ways that array diverges from tabular. The first is that array entries are typeset in math mode, in textstyle (see Modes) except if the cols definition specifies the column with p{...}, which causes the entry to be typeset in text mode. The second is that, instead of tabular’s parameter \tabcolsep, LaTeX’s intercolumn space in an array is governed by \arraycolsep, which gives half the width between columns. The default for this is ‘5pt’ so that between two columns comes 10pt of space.

To obtain arrays with braces the standard is to use the amsmath package. It comes with environments pmatrix for an array surrounded by parentheses (...), bmatrix for an array surrounded by square brackets [...], Bmatrix for an array surrounded by curly braces {...}, vmatrix for an array surrounded by vertical bars |...|, and Vmatrix for an array surrounded by double vertical bars ||...||, along with a number of other array constructs.

The next example uses the amsmath package.

\usepackage{amsmath}  % in preamble

\begin{equation}    
  \begin{vmatrix}{cc}  % array with vert lines
    a  &b \\
    c  &d       
  \end{vmatrix}=ad-bc
\end{equation}

There are many packages concerning arrays. The array package has many useful extensions, including more column types. The dcolumn package adds a column type to center on a decimal point. For both see the documentation on CTAN.

8.3 center

Synopsis:

\begin{center}
  line1 \\
  line2 \\
  ...
\end{center}

Create a new paragraph consisting of a sequence of lines that are centered within the left and right margins. Use double-backslash, \\, to get a line break (see \\). If some text is too long to fit on a line then LaTeX will insert line breaks that avoid hyphenation and avoid stretching or shrinking any interword space.

This environment inserts space above and below the text body. See \centering to avoid such space, for example inside a figure environment.

This example produces three centered lines. There is extra vertical space between the last two lines.

\begin{center}
  A Thesis Submitted in Partial Fufillment \\
  of the Requirements of \\[0.5ex]
  the School of Environmental Engineering
\end{center}

In this example, depending on the page’s line width, LaTeX may choose a line break for the part before the double backslash. If so, it will center each of the two lines and if not it will center the single line. Then LaTeX will break at the double backslash, and will center the ending.

\begin{center}
  My father considered that anyone who went to chapel and didn't drink 
  alcohol was not to be tolerated.\\ 
  I grew up in that belief.  --Richard Burton 
\end{center}

A double backslash after the final line is optional. If present it doesn’t add any vertical space.

In a two-column document the text is centered in a column, not in the entire page.

8.3.1 \centering

Synopsis:

{\centering ... }

or

\begin{group}
  \centering ...
\end{group}

Center the material in its scope. It is most often used inside an environment such as figure, or in a parbox.

This example’s \centering declaration causes the graphic to be horizontally centered.

\begin{figure}
  \centering
  \includegraphics[width=0.6\textwidth]{ctan_lion.png}
  \caption{CTAN Lion}  \label{fig:CTANLion}
\end{figure}

The scope of this \centering ends with the \end{figure}.

Unlike the center environment, the \centering command does not add vertical space above and below the text. That’s its advantage in the above example; there is not an excess of space.

It also does not start a new paragraph; it simply changes how LaTeX formats paragraph units. If ww {\centering xx \\ yy} zz is surrounded by blank lines then LaTeX will create a paragraph whose first line ‘ww xx’ is centered and whose second line, not centered, contains ‘yy zz’. Usually what is desired is for the scope of the declaration to contain a blank line or the \end command of an environment such as figure or table that ends the paragraph unit. Thus, if {\centering xx \\ yy\par} zz is surrounded by blank lines then it makes a new paragraph with two centered lines ‘xx’ and ‘yy’, followed by a new paragraph with ‘zz’ that is formatted as usual.

8.4 description

Synopsis:

\begin{description}
  \item[label of first item] text of first item
  \item[label of second item] text of second item
   ...
\end{description}

Environment to make a list of labeled items. Each item’s label is typeset in bold and is flush left, so that long labels continue into the first line of the item text. There must be at least one item; having none causes the LaTeX error ‘Something's wrong--perhaps a missing \item’.

This example shows the environment used for a sequence of definitions.

\begin{definition}
  \item[lama] A priest.
  \item[llama] A beast.
\end{definition}

The labels ‘lama’ and ‘llama’ are output in boldface, with the left edge on the left margin.

Start list items with the \item command (see \item). Use the optional labels, as in \item[Main point], because there is no sensible default. Following the \item is optional text, which may contain multiple paragraphs.

Since the labels are in bold style, if the label text calls for a font change given in argument style (see Font styles) then it will come out bold. For instance, if the label text calls for typewriter with \item[\texttt{label text}] then it will appear in bold typewriter, if that is available. The simplest way around this, in this example to get non-bold typewriter, is to use declarative style: \item[{\tt label text}]. Similarly, get the standard roman font with \item[{\rm label text}].

For other major LaTeX labelled list environments, see itemize and enumerate. Unlike those environments, nesting description environments does not change the default label; it is boldface and flush left at all levels.

For information about list layout parameters, including the default values, and for information about customizing list layout, see list. The package enumitem is useful for customizing lists.

This example changes the description labels to small caps.

\renewcommand{\descriptionlabel}[1]{%
  {\hspace{\labelsep}\textsc{#1}}}

8.5 displaymath

Synopsis:

\begin{displaymath}
  mathematical text
\end{displaymath}

Environment to typeset the math text on its own line, in display style and centered. To make the text be flush-left use the global option fleqn; see Document class options.

In the displaymath environment no equation number is added to the math text. One way to get an equation number is to use the equation environment (see equation).

LaTeX will not break the math text across lines.

Note that the amsmath package has significantly more extensive displayed equation facilities. For example, there are a number of ways in that package for having math text broken across lines.

The construct \[math text\] is essentially a synonym for \begin{displaymath}math text\end{displaymath} but the latter is easier to work with in the source file; for instance, searching for a square bracket may get false positives but the word displaymath will likely be unique. (The construct $$math text$$ from Plain TeX is sometimes mistakenly used as a synonym for displaymath. It is not a synonym, because the displaymath environment checks that it isn’t started in math mode and that it ends in math mode begun by the matching environment start, because the displaymath environment has different vertical spacing, and because the displaymath environment honors the fleqn option.)

The output from this example is centered and alone on its line.

\begin{displaymath}
  \int_1^2 x^2\,dx=7/3
\end{displaymath}

Also, the integral sign is larger than the inline version \( \int_1^2 x^2\,dx=7/3 \) produces.

8.6 document

The document environment encloses the entire body of a document. It is required in every LaTeX document. See Starting and ending.

8.6.1 \AtBeginDocument

Synopsis:

\AtBeginDocument{code}

Save code and execute it when \begin{document} is executed, at the very end of the preamble. The code is executed after the font selection tables have been set up, so the normal font for the document is the current font. However, the code is executed as part of the preamble so you cannot do any typesetting with it.

You can issue this command more than once; the successive code lines will be executed in the order that you gave them.

8.6.2 \AtEndDocument

Synopsis:

\AtEndDocument{code}

Save code and execute it near the end of the document. Specifically, it is executed when \end{document} is executed, before the final page is finished and before any leftover floating environments are processed. If you want some of the code to be executed after these two processes then include a \clearpage at the appropriate point in code.

You can issue this command more than once; the successive code lines will be executed in the order that you gave them.

8.7 enumerate

Synopsis:

\begin{enumerate}
  \item[optional label of first item] text of first item
  \item[optional label of second item] text of second item
  ...
\end{enumerate}

Environment to produce a numbered list of items. The format of the label numbering depends on the nesting level of this environment; see below. The default top-level numbering is ‘1.’, ‘2.’, etc. Each enumerate list environment must have at least one item; having none causes the LaTeX error ‘Something's wrong--perhaps a missing \item’.

This example gives the first two finishers in the 1908 Olympic marathon. As a top-level list the labels would come out as ‘1.’ and ‘2.’.

\begin{enumerate}
 \item Johnny Hayes (USA)
 \item Charles Hefferon (RSA) 
\end{enumerate}

Start list items with the \item command (see \item). If you give \item an optional argument by following it with square brackets, as in \item[Interstitial label], then the next item will continue the interrupted sequence (see \item). That is, you will get labels like ‘1.’, then ‘Interstitial label’, then ‘2.’. Following the \item is optional text, which may contain multiple paragraphs.

Enumerations may be nested within other enumerate environments, or within any paragraph-making environment such as itemize (see itemize), up to four levels deep. This gives LaTeX’s default for the format at each nesting level, where 1 is the top level, the outermost level.

1. arabic number followed by a period: ‘1.’, ‘2.’, …
2. lowercase letter inside parentheses: ‘(a)’, ‘(b)’ …
3. lowercase roman numeral followed by a period: ‘i.’, ‘ii.’, …
4. uppercase letter followed by a period: ‘A.’, ‘B.’, …

The enumerate environment uses the counters \enumi through \enumiv (see Counters).

For other major LaTeX labeled list environments, see description and itemize. For information about list layout parameters, including the default values, and for information about customizing list layout, see list. The package enumitem is useful for customizing lists.

To change the format of the label use \renewcommand (see \newcommand & \renewcommand) on the commands \labelenumi through \labelenumiv. For instance, this first level list will be labelled with uppercase letters, in boldface, and without a trailing period.

\renewcommand{\labelenumi}{\textbf{\Alph{enumi}}}
\begin{enumerate}
  \item Shows as boldface A
  \item Shows as boldface B
\end{enumerate}

For a list of counter-labeling commands see \alph \Alph \arabic \roman \Roman \fnsymbol.

8.8 eqnarray

The eqnarray environment is obsolete. It has infelicities, including spacing that is inconsistent with other mathematics elements. (See “Avoid eqnarray!” by Lars Madsen http://tug.org/TUGboat/tb33-1/tb103madsen.pdf). New documents should include the amsmath package and use the displayed mathematics environments provided there, such as the align environment. We include a description only for completeness and for working with old documents.

Synopsis:

\begin{eqnarray} 
  first formula left  &first formula middle  &first formula right \\
  ...
\end{eqnarray}

or

\begin{eqnarray*} 
  first formula left  &first formula middle  &first formula right \\
  ...
\end{eqnarray*}

Display a sequence of equations or inequalities. The left and right sides are typeset in display mode, while the middle is typeset in text mode.

It is similar to a three-column array environment, with items within a row separated by an ampersand (&), and with rows separated by double backslash  \\). The starred form of line break (\\*) can also be used to separate equations, and will disallow a page break there (see \\).

The unstarred form eqnarray places an equation number on every line (using the equation counter), unless that line contains a \nonumber command. The starred form eqnarray* omits equation numbering, while otherwise being the same.

The command \lefteqn is used for splitting long formulas across lines. It typesets its argument in display style flush left in a box of zero width.

This example shows three lines. The first two lines make an inequality, while the third line has not entry on the left side.

\begin{eqnarray*}
  \lefteqn{x_1+x_2+\cdots+x_n}     \\
    &\leq &y_1+y_2+\cdots+y_n      \\
    &=    &z+y_3+\cdots+y_n
\end{eqnarray*}

8.9 equation

Synopsis:

\begin{equation}
  mathematical text
\end{equation}

The same as a displaymath environment (see displaymath) except that LaTeX puts an equation number flush to the right margin. The equation number is generated using the equation counter.

You should have no blank lines between \begin{equation} and \begin{equation}, or LaTeX will tell you that there is a missing dollar sign.

The package amsmath package has extensive displayed equation facilities. New documents should include this package.

8.10 figure

Synopsis:

\begin{figure}[placement]
  figure body
  \caption[loftitle]{title}  % optional
  \label{label}              % optional
\end{figure}

or:

\begin{figure*}[placement]
  figure body
  \caption[loftitle]{title}  % optional
  \label{label}              % optional  
\end{figure*}

Figures are for material that is not part of the normal text. An example is material that you cannot have split between two pages, such as a graphic. Because of this, LaTeX does not typeset figures in sequence with normal text but instead “floats” them to a convenient place, such as the top of a following page (see Floats).

The figure body can consist of imported graphics (see Graphics), or text, LaTeX commands, etc. It is typeset in a parbox of width \textwidth.

The possible values of placement are h for ‘here’, t for ‘top’, b for ‘bottom’, and p for ‘on a separate page of floats’. For the effect of these options on the float placement algorithm, see Floats.

The starred form figure* is used when a document is in double-column mode (see \twocolumn). It produces a figure that spans both columns, at the top of the page. To add the possibility of placing at a page bottom see the discussion of placement b in Floats.

The label is optional; it is used for cross references (see Cross references). The optional \caption command specifies caption text for the figure. By default it is numbered. If loftitle is present, it is used in the list of figures instead of title (see Table of contents etc.).

This example makes a figure out of a graphic. LaTeX will place that graphic and its caption at the top of a page or, if it is pushed to the end of the document, on a page of floats.

\usepackage{graphicx}  % in preamble
  ...
\begin{figure}[t]
  \centering
  \includegraphics[width=0.5\textwidth]{CTANlion.png}
  \caption{The CTAN lion, by Duane Bibby}
\end{figure}

8.11 filecontents: Write an external file

Synopsis:

\begin{filecontents}{filename}
  text
\end{filecontents}

or

\begin{filecontents*}{filename}
  text
\end{filecontents*}

Create a file named filename and fill it with text. The unstarred version of the environment filecontents prefixes the content of the created file with a header; see the example below. The starred version filecontents* does not include the header.

This environment can be used anywhere in the preamble, although it often appears before the \documentclass command. It is typically used when a source file requires a nonstandard style or class file. The environment will write that file to the directory containing the source and thus make the source file self-contained. Another use is to include bib references in the file, again to make it self-contained.

The environment checks whether a file of that name already exists and if so, does not do anything. There is a filecontents package that redefines the filecontents environment so that instead of doing nothing in that case, it will overwrite the existing file.

For example, this document

\documentclass{article}
\begin{filecontents}{JH.sty}
\newcommand{\myname}{Jim Hef{}feron}
\end{filecontents}
\usepackage{JH}
\begin{document}
Article by \myname.
\end{document}

produces this file JH.sty.

%% LaTeX2e file `JH.sty'
%% generated by the `filecontents' environment
%% from source `test' on 2015/10/12.
%%
\newcommand{\myname}{Jim Hef{}feron}

8.12 flushleft

Synopsis:

\begin{flushleft}
  line1 \\
  line2 \\
  ...
\end{flushleft}

An environment that creates a paragraph whose lines are flush to the left-hand margin, and ragged right. If you have lines that are too long then LaTeX will linebreak them in a way that avoids hyphenation and stretching or shrinking spaces. To force a new line use a double backslash, \\. For the declaration form see \raggedright.

This creates a box of text that is at most 3 inches wide, with the text flush left and ragged right.

\noindent\begin{minipage}{3in}
\begin{flushleft}
  A long sentence that will be broken by \LaTeX{}
    at a convenient spot. \\
  And, a fresh line forced by the double backslash.
\end{flushleft}
\end{minipage}

8.12.1 \raggedright

Synopses:

{\raggedright  ... }

or

\begin{environment} \raggedright
  ...
\end{environment}

A declaration which causes lines to be flush to the left margin and ragged right. It can be used inside an environment such as quote or in a parbox. For the environment form see flushleft.

Unlike the flushleft environment, the \raggedright command does not start a new paragraph; it only changes how LaTeX formats paragraph units. To affect a paragraph unit’s format, the scope of the declaration must contain the blank line or \end command that ends the paragraph unit.

Here \raggedright in each second column keeps LaTeX from doing very awkward typesetting to fit the text into the narrow column. Note that \raggedright is inside the curly braces {...} to delimit its effect.

\begin{tabular}{rp{2in}}
  Team alpha  &{\raggedright This team does all the real work.} \\
  Team beta   &{\raggedright This team ensures that the water
                cooler is never empty.}                         \\
\end{tabular}

8.13 flushright

\begin{flushright}
  line1 \\
  line2 \\
  ...
\end{flushright}

An environment that creates a paragraph whose lines are flush to the right-hand margin and ragged left. If you have lines that are too long to fit the margins then LaTeX will linebreak them in a way that avoids hyphenation and stretching or shrinking spaces. To force a new line use a double backslash, \\. For the declaration form see \raggedleft.

For an example related to this environment, see flushleft.

8.13.1 \raggedleft

Synopses:

{\raggedleft  ... }

or

\begin{environment} \raggedleft
  ...
\end{environment}

A declaration which causes lines to be flush to the right margin and ragged left. It can be used inside an environment such as quote or in a parbox. For the environment form see flushright.

Unlike the flushright environment, the \raggedleft command does not start a new paragraph; it only changes how LaTeX formats paragraph units. To affect a paragraph unit’s format, the scope of the declaration must contain the blank line or \end command that ends the paragraph unit.

For an example related to this environment, see \raggedright.

8.14 itemize

Synopsis:

\begin{itemize}
  \item[optional label of first item] text of first item
  \item[optional label of second item] text of second item
  ...
\end{itemize}

Produce a list that is unordered, sometimes called a bullet list. The environment must have at least one \item; having none causes the LaTeX error ‘Something's wrong--perhaps a missing \item’.

This gives a two-item list.

\begin{itemize}
 \item Pencil and watercolor sketch by Cassandra
 \item Rice portrait 
\end{itemize}

As a top-level list each label would come out as a bullet, •. The format of the labeling depends on the nesting level; see below.

Start list items with the \item command (see \item). If you give \item an optional argument by following it with square brackets, as in \item[Optional label], then by default it will appear in bold and be flush right, so it could extend into the left margin. For labels that are flush left see the description environment. Following the \item is optional text, which may contain multiple paragraphs.

Itemized lists can be nested within one another, up to four levels deep. They can also be nested within other paragraph-making environments, such as enumerate (see enumerate). The itemize environment uses the commands \labelitemi through \labelitemiv to produce the default label (this also uses the convention of lowercase roman numerals at the end of the command names that signify the nesting level). These are the default marks at each level.

1. • (bullet, from \textbullet)
2. -- (bold en-dash, from \normalfont\bfseries\textendash)
3. * (asterisk, from \textasteriskcentered)
4. . (centered dot, rendered here as a period, from \textperiodcentered)

Change the labels with \renewcommand. For instance, this makes the first level use diamonds.

\renewcommand{\labelitemi}{$\diamond$}

The distance between the left margin of the enclosing environment and the left margin of the itemize list is determined by the parameters \leftmargini through \leftmarginvi. (Note the convention of using lowercase roman numerals a the end of the command name to denote the nesting level.) The defaults are: 2.5em in level 1 (2em in two-column mode), 2.2em in level 2, 1.87em in level 3, and 1.7em in level 4, with smaller values for more deeply nested levels.

For other major LaTeX labeled list environments, see description and enumerate. For information about list layout parameters, including the default values, and for information about customizing list layout, see list. The package enumitem is useful for customizing lists.

This example greatly reduces the margin space for outermost itemized lists.

\setlength{\leftmargini}{1.25em} % default 2.5em

Especially for lists with short items, it may be desirable to elide space between items. Here is an example defining an itemize* environment with no extra spacing between items, or between paragraphs within a single item (\parskip is not list-specific, see \parindent & \parskip):

\newenvironment{itemize*}%
  {\begin{itemize}%
    \setlength{\itemsep}{0pt}%
    \setlength{\parsep}{0pt}}%
    \setlength{\parskip}{0pt}}%
  {\end{itemize}}

8.15 letter environment: writing letters

This environment is used for creating letters. See Letters.

8.16 list

Synopsis:

\begin{list}{labeling}{spacing}
  \item[optional label of first item] text of first item
  \item[optional label of second item] text of second item
  ...
\end{list}

An environment for constructing lists.

Note that this environment does not typically appear in the document body. Most lists created by LaTeX authors are the ones that come standard: the description, enumerate, and itemize environments (see description, enumerate, and itemize).

Instead, the list environment is most often used in macros. For example, many standard LaTeX environments that do not immediately appear to be lists are in fact constructed using list, including quotation, quote, and center (see quotation & quote, see center).

This uses the list environment to define a new custom environment.

\newcounter{namedlistcounter}  % number the items
\newenvironment{named}
  {\begin{list}
     {Item~\Roman{namedlistcounter}.} % labeling 
     {\usecounter{namedlistcounter}   % set counter
      \setlength{\leftmargin}{3.5em}} % set spacing 
  }
  {\end{list}}

\begin{named}
  \item Shows as ``Item~I.''
  \item[Special label.] Shows as ``Special label.''
  \item Shows as ``Item~II.''
\end{named}

The mandatory first argument labeling specifies the default labeling of list items. It can contain text and LaTeX commands, as above where it contains both ‘Item’ and ‘\Roman{...}’. LaTeX forms the label by putting the labeling argument in a box of width \labelwidth. If the label is wider than that, the additional material extends to the right. When making an instance of a list you can override the default labeling by giving \item an optional argument by including square braces and the text, as in the above \item[Special label.]; see \item.

The mandatory second argument spacing has a list of commands. This list can be empty. A command that can go in here is \usecounter{countername} (see \usecounter). Use this to tell LaTeX to number the items using the given counter. The counter will be reset to zero each time LaTeX enters the environment, and the counter is incremented by one each time LaTeX encounters an \item that does not have an optional argument.

Another command that can go in spacing is \makelabel, which constructs the label box. By default it puts the contents flush right. Its only argument is the label, which it typesets in LR mode (see Modes). One example of changing its definition is that to the above named example, before the definition of the environment add \newcommand{\namedmakelabel}[1]{\textsc{#1}}, and between the \setlength command and the parenthesis that closes the spacing argument also add \let\makelabel\namedmakelabel. Then the items will be typeset in small caps. Similarly, changing the second code line to \let\makelabel\fbox puts the labels inside a framed box. Another example of the \makelabel command is below, in the definition of the redlabel environment.

Also often in spacing are commands to redefine the spacing for the list. Below are the spacing parameters with their default values. (Default values for derived environments such as itemize can be different than the values shown here.) See also the figure that follows the list. Each is a length (see Lengths). The vertical spaces are normally rubber lengths, with plus and minus components, to give TeX flexibility in setting the page. Change each with a command such as \setlength{itemsep}{2pt plus1pt minus1pt}. For some effects these lengths should be zero or negative.

\itemindent

Extra horizontal space indentation, beyond leftmargin, of the first line each item. Its default value is 0pt.

\itemsep

Vertical space between items, beyond the \parsep. The defaults for the first three levels in LaTeX’s ‘article’, ‘book’, and ‘report’ classes at 10 point size are: 4pt plus2pt minus1pt, \parsep (that is, 2pt plus1pt minus1pt), and \topsep (that is, 2pt plus1pt minus1pt). The defaults at 11 point are: 4.5pt plus2pt minus1pt, \parsep (that is, 2pt plus1pt minus1pt), and topsep (that is, 2pt plus1pt minus1pt). The defaults at 12 point are: 5pt plus2.5pt minus1pt, \parsep (that is, 2.5pt plus1pt minus1pt), and \topsep (that is, 2.5pt plus1pt minus1pt).

\labelsep

Horizontal space between the label and text of an item. The default for LaTeX’s ‘article’, ‘book’, and ‘report’ classes is 0.5em.

\labelwidth

Horizontal width. The box containing the label is nominally this wide. If \makelabel returns text that is wider than this then the first line of the item will be indented to make room for this extra material. If \makelabel returns text of width less than or equal to \labelwidth then LaTeX’s default is that the label is typeset flush right in a box of this width.

The left edge of the label box is \leftmargin+\itemindent-\labelsep-\labelwidth from the left margin of the enclosing environment.

The default for LaTeX’s ‘article’, ‘book’, and ‘report’ classes at the top level is \leftmargini-\labelsep, (which is 2em in one column mode and 1.5em in two column mode). At the second level it is \leftmarginii-\labelsep, and at the third level it is \leftmarginiii-\labelsep. These definitions make the label’s left edge coincide with the left margin of the enclosing environment.

\leftmargin

Horizontal space between the left margin of the enclosing environment (or the left margin of the page if this is a top-level list), and the left margin of this list. It must be non-negative.

In the standard LaTeX document classes, a top-level list has this set to the value of \leftmargini, while a list that is nested inside a top-level list has this margin set to \leftmarginii. More deeply nested lists get the values of \leftmarginiii through \leftmarginvi. (Nesting greater than level five generates the error message ‘Too deeply nested’.)

The defaults for the first three levels in LaTeX’s ‘article’, ‘book’, and ‘report’ classes are: \leftmargini is 2.5em (in two column mode, 2em), \leftmarginii is 2.2em, and \leftmarginiii is 1.87em.

\listparindent

Horizontal space of additional line indentation, beyond \leftmargin, for second and subsequent paragraphs within a list item. A negative value makes this an “outdent”. Its default value is 0pt.

\parsep

Vertical space between paragraphs within an item. In the ‘book’ and ‘article’ classes The defaults for the first three levels in LaTeX’s ‘article’, ‘book’, and ‘report’ classes at 10 point size are: 4pt plus2pt minus1pt, 2pt plus1pt minus1pt, and 0pt. The defaults at 11 point size are: 4.5pt plus2pt minus1pt, 2pt plus1pt minus1pt, and 0pt. The defaults at 12 point size are: 5pt plus2.5pt minus1pt, 2.5pt plus1pt minus1pt, and 0pt.

\partopsep

Vertical space added, beyond \topsep+\parskip, to the top and bottom of the entire environment if the list instance is preceded by a blank line. (A blank line in the LaTeX source before the list changes spacing at both the top and bottom of the list; whether the line following the list is blank does not matter.)

The defaults for the first three levels in LaTeX’s ‘article’, ‘book’, and ‘report’ classes at 10 point size are: 2pt plus1 minus1pt, 2pt plus1pt minus1pt, and 1pt plus0pt minus1pt. The defaults at 11 point are: 3pt plus1pt minus1pt, 3pt plus1pt minus1pt, and 1pt plus0pt minus1pt). The defaults at 12 point are: 3pt plus2pt minus3pt, 3pt plus2pt minus2pt, and 1pt plus0pt minus1pt.

\rightmargin

Horizontal space between the right margin of the list and the right margin of the enclosing environment. Its default value is 0pt. It must be non-negative.

\topsep

Vertical space added to both the top and bottom of the list, in addition to \parskip (see \parindent & \parskip). The defaults for the first three levels in LaTeX’s ‘article’, ‘book’, and ‘report’ classes at 10 point size are: 8pt plus2pt minus4pt, 4pt plus2pt minus1pt, and 2pt plus1pt minus1pt. The defaults at 11 point are: 9pt plus3pt minus5pt, 4.5pt plus2pt minus1pt, and 2pt plus1pt minus1pt. The defaults at 12 point are: 10pt plus4pt minus6pt, 5pt plus2.5pt minus1pt, and 2.5pt plus1pt minus1pt.

This shows the horizontal and vertical distances.

The lengths shown are listed below. The key relationship is that the right edge of the bracket for h1 equals the right edge of the bracket for h4, so that the left edge of the label box is at h3+h4-(h0+h1).

v0

\topsep + \parskip if the list environment does not start a new paragraph, and \topsep+\parskip+\partopsep if it does

v1

\parsep

v2

\itemsep+\parsep

v3

Same as v0. (This space is affected by whether a blank line appears in the source above the environment; whether a blank line appears in the source below the environment does not matter.)

h0

\labelwidth

h1

\labelsep

h2

\listparindent

h3

\leftmargin

h4

\itemindent

h5

\rightmargin

The list’s left and right margins, shown above as h3 and h5, are with respect to the ones provided by the surrounding environment, or with respect to the page margins for a top-level list. The line width used for typesetting the list items is \linewidth (see Page layout parameters). For instance, set the list’s left margin to be one quarter of the distance between the left and right margins of the enclosing environment with \setlength{\leftmargin}{0.25\linewidth}.

Page breaking in a list structure is controlled by the three parameters below. For each, the LaTeX default is -\@lowpenalty, that is, -51. Because it is negative, it somewhat encourages a page break at each spot. Change it with, e.g., \@beginparpenalty=9999; a value of 10000 prohibits a page break.

\@beginparpenalty

The page breaking penalty for breaking before the list (default -51).

\@itempenalty

The page breaking penalty for breaking before a list item (default -51).

\@endparpenalty

The page breaking penalty for breaking after a list (default -51).

The package enumitem is useful for customizing lists.

This example has the labels in red. They are numbered, and the left edge of the label lines up with the left edge of the item text. See \usecounter.

\usepackage{color}
\newcounter{cnt}  
\newcommand{\makeredlabel}[1]{\textcolor{red}{#1.}}
\newenvironment{redlabel}
  {\begin{list}
    {\arabic{cnt}}
    {\usecounter{cnt}
     \setlength{\labelwidth}{0em}
     \setlength{\labelsep}{0.5em}
     \setlength{\leftmargin}{1.5em}
     \setlength{\itemindent}{0.5em} % equals \labelwidth+\labelsep
     \let\makelabel=\makeredlabel
    }
  }
{\end{list} }

8.16.1 \item: An entry in a list

Synopsis:

\item text of item

or

\item[optional-label] text of item

An entry in a list. The entries are prefixed by a label, whose default depends on the list type.

Because the optional label is surrounded by square brackets ‘[...]’, if you have an item whose text starts with ‘[’, you have to hide the bracket inside curly braces, as in: \item {[} is an open square bracket; otherwise, LaTeX will think it marks the start of an optional label.

Similarly, if the item does have the optional label and you need a close square bracket inside that label, you must hide it in the same way: \item[Close square bracket, {]}]. See LaTeX command syntax.

In this example the enumerate list has two items that use the default label and one that uses the optional label.

\begin{enumerate}
  \item Moe
  \item[sometimes] Shemp
  \item Larry
\end{enumerate}

The first item is labelled ‘1.’, the second item is labelled ‘sometimes’, and the third item is labelled ‘2.’. Because of the optional label in the second item, the third item is not labelled ‘3.’.

8.16.2 trivlist: A restricted form of list

Synopsis:

\begin{trivlist}
  ...
\end{trivlist}

A restricted version of the list environment, in which margins are not indented and an \item without an optional argument produces no text. It is most often used in macros, to define an environment where the \item command as part of the environment’s definition. For instance, the center environment is defined essentially like this:

\newenvironment{center}
  {\begin{trivlist}\centering\item\relax}
  {\end{trivlist}}

Using trivlist in this way allows the macro to inherit some common code: combining vertical space of two adjacent environments; detecting whether the text following the environment should be considered a new paragraph or a continuation of the previous one; adjusting the left and right margins for possible nested list environments.

Specifically, trivlist uses the current values of the list parameters (see list), except that \parsep is set to the value of \parskip, and \leftmargin, \labelwidth, and \itemindent are set to zero.

This example outputs the items as two paragraphs, except that (by default) they have no paragraph indent and are vertically separated.

\begin{trivlist}
\item The \textit{Surprise} is not old; no one would call her old.
\item She has a bluff bow, lovely lines.
\end{trivlist}

8.17 math

Synopsis:

\begin{math}
math
\end{math}

The math environment inserts given math material within the running text. \(...\) and $...$ are synonyms. See Math formulas.

8.18 minipage

Synopses:

\begin{minipage}{width}
  contents
\end{minipage}

or

\begin{minipage}[position][height][inner-pos]{width}
  contents
\end{minipage}

Put contents into a box that is width wide. This is like a small version of a page; it can contain its own footnotes, itemized lists, etc. (There are some restrictions, including that it cannot have floats.) This box will not be broken across pages. So minipage is similar to \parbox (see \parbox) but here you can have paragraphs.

This example will be 3 inches wide, and has two paragraphs.

\begin{minipage}{3in}
  Stephen Kleene was a founder of the Theory of Computation.

  He was a student of Church, wrote three influential texts,
  was President of the Association for Symbolic Logic,
  and won the National Medal of Science.
\end{minipage}

See below for a discussion of the paragraph indent inside a minipage.

The required argument width is a rigid length (see Lengths). It gives the width of the box into which contents are typeset.

There are three optional arguments, position, height, and inner-pos. You need not include all three. For example, get the default position and set the height with \begin{minipage}[c][2.54cm] contents \end{minipage}. (Get the natural height with an empty argument, [].)

The optional argument position governs how the minipage vertically aligns with the surrounding material.

c

(synonym m) Default. Positions the minipage so its vertical center lines up with the center of the adjacent text line (what Plain TeX calls \vcenter).

t

Match the top line in the minipage with the baseline of the surrounding text (Plain TeX’s \vtop.

b

Match the bottom line in the minipage with the baseline of the surrounding text (Plain TeX’s \vbox.

To see the effects of these, contrast running this

---\begin{minipage}[c]{0.25in}
  first\\ second\\ third
\end{minipage}

with the results of changing c to b or t.

The optional argument height is a rigid length (see Lengths). It sets the height of the minipage. You can enter any value larger than, or equal to, or smaller than the minipage’s natural height and LaTeX will not give an error or warning. You can also set it to a height of zero or a negative value.

The final optional argument inner-pos controls the placement of content inside the box. These are the possible values are (the default is the value of position).

t

Place content at the top of the box.

c

Place it in the vertical center.

b

Place it at the box bottom.

s

Stretch contents out vertically; it must contain vertically stretchable space.

The inner-pos argument makes sense when the height option is set to a value larger than the minipage’s natural height. To see the effect of the options, run this example with the various choices in place of b.

Text before
\begin{center}
  ---\begin{minipage}[c][3in][b]{0.25\textwidth}
       first\\ second\\ third
  \end{minipage}              
\end{center}
Text after  

By default paragraphs are not indented in a minipage. Change that with a command such as \setlength{\parindent}{1pc} at the start of contents.

Footnotes in a minipage environment are handled in a way that is particularly useful for putting footnotes in figures or tables. A \footnote or \footnotetext command puts the footnote at the bottom of the minipage instead of at the bottom of the page, and it uses the \mpfootnote counter instead of the ordinary footnote counter (see Counters).

This puts the footnote at the bottom of the table, not the bottom of the page.

\begin{center}           % center the minipage on the line
\begin{minipage}{2.5in}
  \begin{center}         % center the table inside the minipage
    \begin{tabular}{ll}
      \textsc{Monarch}  &\textsc{Reign}             \\ \hline
      Elizabeth II      &63 years\footnote{to date} \\
      Victoria          &63 years                   \\
      George III        &59 years
    \end{tabular}
  \end{center}  
\end{minipage}
\end{center}

If you nest minipages then there is an oddness when using footnotes. Footnotes appear at the bottom of the text ended by the next \end{minipage} which may not be their logical place.

This puts a table containing data side by side with a map graphic. They are vertically centered.

\newcommand*{\vcenteredhbox}[1]{\begin{tabular}{@{}c@{}}#1\end{tabular}}
  ...
\begin{center}
  \vcenteredhbox{\includegraphics[width=0.3\textwidth]{nyc.png}}
  \hspace{0.1\textwidth}
  \begin{minipage}{0.5\textwidth}
    \begin{tabular}{r|l}
      \multicolumn{1}{r}{Borough} &Pop (million)  \\ \hline
      The Bronx      &$1.5$  \\
      Brooklyn       &$2.6$  \\
      Manhattan      &$1.6$  \\
      Queens         &$2.3$  \\
      Staten Island  &$0.5$  
    \end{tabular}
  \end{minipage}              
\end{center}

8.19 picture

Synopses:

\begin{picture}(width,height)
   picture commands 
\end{picture}

or

\begin{picture}(width,height)(xoffset,yoffset)
  picture commands
\end{picture}

An environment to create simple pictures containing lines, arrows, boxes, circles, and text. Note that while this environment is not obsolete, new documents typically use much more powerful graphics creation systems, such as TikZ, PSTricks, MetaPost, or Asymptote. These are not covered in this document; see CTAN.

This shows the parallelogram law for adding vectors.

\setlength{\unitlength}{1cm}
\begin{picture}(6,6)      % picture box will be 6cm wide by 6cm tall
  \put(0,0){\vector(2,1){4}}  % for every 2 over this vector goes 1 up
    \put(2,1){\makebox(0,0)[l]{\ first leg}}
  \put(4,2){\vector(1,2){2}}
    \put(5,4){\makebox(0,0)[l]{\ second leg}}  
  \put(0,0){\line(1,1){6}}
    \put(3,3){\makebox(0,0)[r]{sum\ }}  
\end{picture}

You can also use this environment to place arbitrary material at an exact location.

\usepackage{color,graphicx}  % in preamble
  ...
\begin{center}
\setlength{\unitlength}{\textwidth} 
\begin{picture}(1,1)      % leave space, \textwidth wide and tall
  \put(0,0){\includegraphics[width=\textwidth]{desertedisland.jpg}}
  \put(0.25,0.35){\textcolor{red}{X Treasure here}}
\end{picture}
\end{center}

The red X will be precisely a quarter of the \linewidth from the left margin, and 0.35\linewidth up from the bottom. Another example of this usage is to put similar code in the page header to get repeat material on each of a document’s pages.

The picture environment has one required argument, a pair of numbers (width,height). Multiply these by the value \unitlength to get the nominal size of the output, the space that LaTeX reserves on the output page. This nominal size need not be how large the picture really is; LaTeX will draw things from the picture outside the picture’s box.

This environment also has an optional argument (xoffset,yoffset). It is used to shift the origin. Unlike most optional arguments, this one is not contained in square brackets. As with the required argument, it consists of two real numbers. Multiply these by \unitlength to get the point at the lower-left corner of the picture.

For example, if \unitlength has been set to 1mm, the command

\begin{picture}(100,200)(10,20)

produces a box of width 100 millimeters and height 200 millimeters. The picture’s origin is the point (10mm,20mm) and so the lower-left corner is there, and the upper-right corner is at (110mm,220mm). When you first draw a picture you typically omit the optional argument, leaving the origin at the lower-left corner. If you then want to modify your picture by shifting everything, you can just add the appropriate optional argument.

Each picture command tells LaTeX where to put something by naming its position. A position is a pair such as (2.4,-5) giving the x- and y-coordinates. A coordinate is a not a length, it is a real number (it may have a decimal point or a minus sign). It specifies a length in multiples of the unit length \unitlength, so if \unitlength has been set to 1cm, then the coordinate 2.54 specifies a length of 2.54 centimeters.

LaTeX’s default for \unitlength is 1pt. it is a rigid length (see Lengths). Change it with the \setlength command (see \setlength). Make this change only outside of a picture environment.

Coordinates are given with respect to an origin, which is normally at the lower-left corner of the picture. Note that when a position appears as an argument, as with \put(1,2){...}, it is not enclosed in braces since the parentheses serve to delimit the argument. Also, unlike in some computer graphics systems, larger y-coordinates are further up the page.

There are four ways to put things in a picture: \put, \multiput, \qbezier, and \graphpaper. The most often used is \put. This

\put(11.3,-0.3){...}

places the object with its reference point at coordinates (11.3,-0.3). The reference points for various objects will be described below. The \put command creates an LR box (see Modes). Anything that can go in an \mbox (see \mbox & \makebox) can go in the text argument of the \put command. The reference point will be the lower left corner of the box. In this picture

\setlength{\unitlength}{1cm}
...\begin{picture}(1,1)
  \put(0,0){\line(1,0){1}}
  \put(0,0){\line(1,1){1}}
\end{picture}

the three dots are just slightly left of the point of the angle formed by the two lines. (Also, \line(1,1){1} does not call for a line of length one; rather the line has a change in the x coordinate of 1.)

The \multiput, qbezier, and graphpaper commands are described below.

This draws a rectangle with a wavy top, using \qbezier for that curve.

\begin{picture}(3,1.5)
  \put(0,0){\vector(1,0){8}}  % x axis
  \put(0,0){\vector(0,1){4}}  % y axis
  \put(2,0){\line(0,1){3}}       % left side rectangle
  \put(4,0){\line(0,1){3.5}}     % right side
  \qbezier(2,3)(2.5,2.9)(3,3.25)
    \qbezier(3,3.25)(3.5,3.6)(4,3.5)
  \thicklines                 % below here, lines are twice as thick
  \put(2,3){\line(4,1){2}}
  \put(4.5,2.5){\framebox{Trapezoidal Rule}}
\end{picture}

8.19.1 \put

Synopsis:

\put(xcoord,ycoord){content}

Place content at the coordinate (xcoord,ycoord). See the discussion of coordinates and \unitlength in picture. The content is processed in LR mode (see Modes) so it cannot contain line breaks.

This includes the text into the picture.

\put(4.5,2.5){Apply the \textit{unpoke} move}

The reference point, the location (4.5,2.5), is the lower left of the text, at the bottom left of the ‘A’.

8.19.2 \multiput

Synopsis:

\multiput(x,y)(delta_x,delta_y){num-copies}{obj}

Copy obj a total of num-copies times, with an increment of delta_x,delta_y. The obj first appears at position (x,y), then at (x+\delta_x,y+\delta_y), and so on.

This draws a simple grid with every fifth line in bold (see also \graphpaper).

\begin{picture}(10,10)
  \linethickness{0.05mm}
  \multiput(0,0)(1,0){10}{\line(0,1){10}} 
  \multiput(0,0)(0,1){10}{\line(1,0){10}}
  \linethickness{0.5mm}
  \multiput(0,0)(5,0){3}{\line(0,1){10}}
  \multiput(0,0)(0,5){3}{\line(1,0){10}}
\end{picture}

8.19.3 \qbezier

Synopsis:

\qbezier(x1,y1)(x2,y2)(x3,y3)
\qbezier[num](x1,y1)(x2,y2)(x3,y3)

Draw a quadratic Bezier curve whose control points are given by the three required arguments (x1,y1), (x2,y2), and (x3,y3). That is, the curve runs from (x1,y1) to (x3,y3), is quadratic, and is such that the tangent line at (x1,y1) passes through (x2,y2), as does the tangent line at (x3,y3).

This draws a curve from the coordinate (1,1) to (1,0).

\qbezier(1,1)(1.25,0.75)(1,0)  

The curve’s tangent line at (1,1) contains (1.25,0.75), as does the curve’s tangent line at (1,0).

The optional argument num gives the number of calculated intermediate points. The default is to draw a smooth curve whose maximum number of points is \qbeziermax (change this value with \renewcommand).

8.19.4 \graphpaper

Synopsis:

\graphpaper(x_init,y_init)(x_dimen,y_dimen)
\graphpaper[spacing](x_init,y_init)(x_dimen,y_dimen)

Draw a coordinate grid. Requires the graphpap package. The grid’s origin is (x_init,y_init). Grid lines come every spacing units (the default is 10). The grid extends x_dimen units to the right and y_dimen units up. All arguments must be positive integers.

This make a grid with seven vertical lines and eleven horizontal lines.

\usepackage{graphpap}    % in preamble
  ...
\begin{picture}(6,20)    % in document body
  \graphpaper[2](0,0)(12,20)
\end{picture}

The lines are numbered every ten units.

8.19.5 \line

Synopsis:

\line(x_run,y_rise){travel}

Draw a line. It slopes such that it vertically rises y_rise for every horizontal x_run. The travel is the total horizontal change — it is not the length of the vector, it is the change in x. In the special case of vertical lines, where (x_run,y_rise)=(0,1), the travel gives the change in y.

This draws a line starting at coordinates (1,3).

\put(1,3){\line(2,5){4}}

For every over 2, this line will go up 5. Because travel specifies that this goes over 4, it must go up 10. Thus its endpoint is (1,3)+(4,10)=(5,13). In particular, note that travel=4 is not the length of the line, it is the change in x.

The arguments x_run and y_rise are integers that can be positive, negative, or zero. (If both are 0 then LaTeX treats the second as 1.) With \put(x_init,y_init){\line(x_run,y_rise){travel}}, if x_run is negative then the line’s ending point has a first coordinate that is less than x_init. If y_rise is negative then the line’s ending point has a second coordinate that is less than y_init.

If travel is negative then you get LaTeX Error: Bad \line or \vector argument.

Standard LaTeX can only draw lines with a limited range of slopes because these lines are made by putting together line segments from pre-made fonts. The two numbers x_run and y_rise must have integer values from -6 through 6. Also, they must be relatively prime, so that (x_run,y_rise) can be (2,1) but not (4,2) (if you choose the latter then instead of lines you get sequences of arrowheads; the solution is to switch to the former). To get lines of arbitrary slope and plenty of other shapes in a system like picture, see the package pict2e on CTAN. Another solution is to use a full-featured graphics system such as TikZ, or PSTricks, or MetaPost, or Asymptote

8.19.6 \linethickness

Synopsis:

\linethickness{dim}

Declares the thickness of subsequent horizontal and vertical lines in a picture to be dim, which must be a positive length (see Lengths). It differs from \thinlines and \thicklines in that it does not affect the thickness of slanted lines, circles, or ovals.

8.19.7 \thinlines

Declaration to set the thickness of subsequent lines, circles, and ovals in a picture environment to be 0.4pt. This is the default thickness, so this command is unnecessary unless the thickness has been changed with either \linethickness or \thicklines.

8.19.8 \thicklines

Declaration to set the thickness of subsequent lines, circles, and ovals in a picture environment to be 0.8pt. See also \linethickness and \thinlines. This command is illustrated in the Trapezoidal Rule example of picture.

8.19.9 \circle

Synopsis:

\circle{diameter}
\circle*{diameter}

Produces a circle with a diameter as close as possible to the specified one. The * form produces a filled-in circle.

This draws a circle of radius 6, centered at (5,7).

\put(5,7){\circle{6}}

The available radii for circle are, in points, the even numbers from 2 to 20, inclusive. For circle* they are all the integers from 1 to 15.

8.19.10 \oval

Synopsis:

\oval(width,height)
\oval(width,height)[portion]

Produce a rectangle with rounded corners. The optional argument portion allows you to produce only half or a quarter of the oval. For half an oval take portion to be one of these.

t

top half

b

bottom half

r

right half

l

left half

Produce only one quarter of the oval by setting portion to tr, br, bl, or tl.

This draws the top half of an oval that is 3 wide and 7 tall.

\put(5,7){\oval(3,7)[t]}

The (5,7) is the center of the entire oval, not just the center of the top half.

These shapes are not ellipses. They are rectangles whose corners are made with quarter circles. These circles have a maximum radius of 20pt (see \circle for the sizes). Thus large ovals are just boxes with a small amount of corner rounding.

8.19.11 \shortstack

Synopsis:

\shortstack[position]{line 1 \\ ... }

Produce a vertical stack of objects.

This labels the y axis.

\put(0,0){\vector(1,0){4}}   % x axis
\put(0,0){\vector(0,1){2}}   % y
\put(-0.25,2){\makebox[0][r]{\shortstack[r]{$y$\\ axis}}}

For a short stack, the reference point is the lower left of the stack. In the above example the \mbox & \makebox puts the stack flush right in a zero width box so in total the short stack sits slightly to the left of the y axis.

The valid positions are:

r

Make objects flush right

l

Make objects flush left

c

Center objects (default)

Separate objects into lines with \\. These stacks are short in that, unlike in a tabular or array environment, here the rows are not spaced out to be of even heights. Thus, in \shortstack{X\\o\\o\\X} the first and last rows are taller than the middle two. You can adjust row heights either by putting in the usual interline spacing with \shortstack{X\\ \strut o\\o\\X}, or by hand, via an explicit zero-width box \shortstack{X \\ \rule{0pt}{12pt} o\\o\\X} or by using \\’s optional argument \shortstack{X\\[2pt] o\\o\\X}.

The \shortstack command is also available outside the picture environment.

8.19.12 \vector

Synopsis:

\vector(x_run,y_rise){travel}

Draw a line ending in an arrow. The slope of that line is: it vertically rises y_rise for every horizontal x_run. The travel is the total horizontal change — it is not the length of the vector, it is the change in x. In the special case of vertical vectors, if (x_run,y_rise)=(0,1), then travel gives the change in y.

For an example see picture.

For elaboration on x_run and y_rise see \line. As there, the values of x_run and y_rise are limited. For \vector you must chooses integers between -4 and 4, inclusive. Also, the two you choose must be relatively prime. Thus, \vector(2,1){4} is acceptable but \vector(4,2){4} is not (if you use the latter then you get a sequence of arrowheads).

8.19.13 \makebox (picture)

Synopsis:

\makebox(rec-width,rec-height){text}
\makebox(rec-width,rec-height)[position]{text}

Make a box to hold text. This command fits with the picture environment, although you can use it outside of there, because rec-width and rec-height are numbers specifying distances in terms of the \unitlength (see picture). This command is similar to the normal \makebox command (see \mbox & \makebox) except here that you must specify the width and height. This command is fragile (see \protect).

This makes a box of length 3.5 times \unitlength and height 4 times \unitlength.

\put(1,2){\makebox(3.5,4){...}}

The optional argument position specifies where in the box the text appears. The default is to center it, both horizontally and vertically. To place it somewhere else, use a string with one or two of these letters.

t

Puts text the top of the box.

b

Put text at the bottom.

l

Put text on the left.

r

Put text on the right.

8.19.14 \framebox (picture)

Synopsis:

\framebox(rec-width,rec-height){text}
\framebox(rec-width,rec-height)[position]{text}

This is the same as \makebox (picture) except that it puts a frame around the outside of the box that it creates. The reference point is the bottom left corner of the frame. This command fits with the picture environment, although you can use it outside of there, because lengths are numbers specifying the distance in terms of the \unitlength (see picture). This command is fragile (see \protect).

This example creates a frame 2.5 inches by 3 inches and puts the text in the center.

\setlength{\unitlength}{1in}
\framebox(2.5,3){test text}

The required arguments are that the rectangle has overall width rect-width units and height rect-height units.

The optional argument position specifies the position of text; see \makebox (picture) for the values that it can take.

The rule has thickness \fboxrule and there is a blank space \fboxsep between the frame and the contents of the box.

For this command, you must specify the width and height. If you want to just put a frame around some contents whose dimension is determined in some other way then either use \fbox (see \fbox & \framebox) or \frame (see \frame).

8.19.15 \frame

Synopsis:

\frame{contents}

Puts a rectangular frame around contents. The reference point is the bottom left corner of the frame. In contrast to \framebox (see \framebox (picture)), this command puts no extra space is put between the frame and the object. It is fragile (see \protect).

8.19.16 \dashbox

Synopsis:

\dashbox{dash-len}(rect-width,rect-height){text}
\dashbox{dash-len}(rect-width,rect-height)[position]{text}

Create a dashed rectangle around text. This command fits with the picture environment, although you can use it outside of there, because lengths are numbers specifying the distance in terms of the \unitlength (see picture).

The required arguments are: dashes are dash-len units long, with the same length gap, and the rectangle has overall width rect-width units and height rect-height units.

The optional argument position specifies the position of text; see \makebox (picture) for the values that it can take.

This shows that you can use non-integer value for dash-len.

\put(0,0){\dashbox{0.1}(5,0.5){My hovercraft is full of eels.}}

Each dash will be 0.1\unitlength long, the box’s width is 5\unitlength and its height is 0.5\unitlength.

As in that example, a dashed box looks best when rect-width and rect-height are multiples of the dash-len.

8.20 quotation & quote

Synopsis:

\begin{quotation}
  text
\end{quotation}

or

\begin{quote}
  text
\end{quote}

Include a quotation. Both environments indent margins on both sides by \leftmargin and the text is right-justified.

They differ in how they treat paragraphs. In the quotation environment, paragraphs are indented by 1.5em and the space between paragraphs is small, 0pt plus 1pt. In the quote environment, paragraphs are not indented and there is vertical space between paragraphs (it is the rubber length \parsep).

\begin{quotation} \small\it
  Four score and seven years ago
  ... shall not perish from the earth.
  \hspace{1em plus 1fill}---Abraham Lincoln
\end{quotation}

8.21 tabbing

Synopsis:

\begin{tabbing}
row1col1 \= row1col2 ...  \\
row2col1 \> row2col2 ...  \\
...
\end{tabbing}

Align text in columns, by setting tab stops and tabbing to them much as was done on a typewriter. This is less often used than the environments tabular (see tabular) or array (see array) because in those the width of each column need not be constant and need not be known in advance.

This example has a first line where the tab stops are set to explicit widths, ended by a \kill command (which is described below):

\begin{tabbing}
\hspace{0.75in}     \= \hspace{0.40in}  \= \hspace{0.40in}    \kill
Ship                \> Guns             \> Year    \\ 
\textit{Sophie}     \> 14               \> 1800    \\
\textit{Polychrest} \> 24               \> 1803    \\
\textit{Lively}     \> 38               \> 1804    \\
\textit{Surprise}   \> 28               \> 1805    \\
\end{tabbing}

Both the tabbing environment and the more widely-used tabular environment put text in columns. The most important distinction is that in tabular the width of columns is determined automatically by LaTeX, while in tabbing the user sets the tab stops. Another distinction is that tabular generates a box, but tabbing can be broken across pages. Finally, while tabular can be used in any mode, tabbing can be used only in paragraph mode and it starts a new paragraph.

A tabbing environment always starts a new paragraph, without indentation. Moreover, as shown in the example above, there is no need to use the starred form of the \hspace command at the beginning of a tabbed row. The right margin of the tabbing environment is the end of line, so that the width of the environment is \linewidth.

The tabbing environment contains a sequence of tabbed rows. The first tabbed row begins immediately after \begin{tabbing} and each row ends with \\ or \kill. The last row may omit the \\ and end with just \end{tabbing}.

At any point the tabbing environment has a current tab stop pattern, a sequence of n > 0 tab stops, numbered 0, 1, etc. These create n corresponding columns. Tab stop 0 is always the left margin, defined by the enclosing environment. Tab stop number i is set if it is assigned a horizontal position on the page. Tab stop number i can only be set if all the stops 0, …, i-1 have already been set; normally later stops are to the right of earlier ones.

By default any text typeset in a tabbing environment is typeset ragged right and left-aligned on the current tab stop. Typesetting is done in LR mode (see Modes).

The following commands can be used inside a tabbing environment. They are all fragile (see \protect).

\\ (tabbing)

End a tabbed line and typeset it.

\= (tabbing)

Sets a tab stop at the current position.

\> (tabbing)

Advances to the next tab stop.

\<

Put following text to the left of the local margin (without changing the margin). Can only be used at the start of the line.

\+

Moves the left margin of the next and all the following commands one tab stop to the right, beginning tabbed line if necessary.

\-

Moves the left margin of the next and all the following commands one tab stop to the left, beginning tabbed line if necessary.

\' (tabbing)

Moves everything that you have typed so far in the current column, i.e., everything from the most recent \>, \<, \', \\, or \kill command, to the previous column and aligned to the right, flush against the current column’s tab stop.

\` (tabbing)

Allows you to put text flush right against any tab stop, including tab stop 0. However, it can’t move text to the right of the last column because there’s no tab stop there. The \` command moves all the text that follows it, up to the \\ or \end{tabbing} command that ends the line, to the right margin of the tabbing environment. There must be no \> or \' command between the \` and the \\ or \end{tabbing} command that ends the line.

\a (tabbing)

In a tabbing environment, the commands \=, \' and \` do not produce accents as usual (see Accents). Instead, use the commands \a=, \a' and \a`.

\kill

Sets tab stops without producing text. Works just like \\ except that it throws away the current line instead of producing output for it. Any \=, \+ or \- commands in that line remain in effect.

\poptabs

Restores the tab stop positions saved by the last \pushtabs.

\pushtabs

Saves all current tab stop positions. Useful for temporarily changing tab stop positions in the middle of a tabbing environment.

\tabbingsep

Distance of the text moved by \' to left of current tab stop.

This example typesets a Pascal function:

\begin{tabbing}
function \= fact(n : integer) : integer;\\
         \> begin \= \+ \\
               \> if \= n > 1 then \+ \\
                        fact := n * fact(n-1) \- \\
                  else \+ \\
                        fact := 1; \-\- \\
            end;\\
\end{tabbing}

The output looks like this.

function fact(n : integer) : integer;
         begin
               if n > 1 then
                  fact := n * fact(n-1);
               else
                  fact := 1;
         end;

This example is just for illustration of the environment. To actually typeset computer code in typewriter like this, a verbatim environment (see verbatim) would normally be best. For pretty-printed code, there are quite a few packages, including algorithm2e, fancyvrb, listings, and minted.

8.22 table

Synopsis:

\begin{table}[placement]
  table body
  \caption[loftitle]{title}  % optional
  \label{label}              % also optional
\end{table}

A class of floats (see Floats). They cannot be split across pages and so they are not typeset in sequence with the normal text but instead are floated to a convenient place, such as the top of a following page.

This example table environment contains a tabular

\begin{table}
  \centering\small
  \begin{tabular}{ll}
    \multicolumn{1}{c}{\textit{Author}}
      &\multicolumn{1}{c}{\textit{Piece}}  \\ \hline
    Bach            &Cello Suite Number 1  \\
    Beethoven       &Cello Sonata Number 3 \\
    Brahms          &Cello Sonata Number 1
  \end{tabular}
  \caption{Top cello pieces}
  \label{tab:cello}
\end{table}

but you can put many different kinds of content in a table, including text, LaTeX commands, etc.

For the possible values of placement and their effect on the float placement algorithm, see Floats.

The table body is typeset in a parbox of width \textwidth. It can contain text, commands, graphics, etc.

The label is optional; it is used for cross references (see Cross references). The \caption command is also optional. It specifies caption text for the table. By default it is numbered. If its optional lottitle is present then that text is used in the list of tables instead of title (see Table of contents etc.).

In this example the table and caption will float to the bottom of a page, unless it is pushed to a float page at the end.

\begin{table}[b]
  \centering
  \begin{tabular}{r|p{2in}} \hline
    One &The loneliest number \\
    Two &Can be as sad as one.
         It's the loneliest number since the number one.
  \end{tabular}
  \caption{Cardinal virtues}
  \label{tab:CardinalVirtues}
\end{table}

8.23 tabular

Synopsis:

\begin{tabular}[pos]{cols}
  column 1 entry  &column 2 entry  ...  &column n entry \\
  ...
\end{tabular}

or

\begin{tabular*}{width}[pos]{cols}
  column 1 entry  &column 2 entry  ...  &column n entry \\
  ...
\end{tabular*}

Produce a table, a box consisting of a sequence of horizontal rows. Each row consists of items that are aligned vertically in columns. This illustrates many of the features.

\begin{tabular}{l|l}
  \textit{Player name}  &\textit{Career home runs}  \\ 
  \hline
  Hank Aaron  &755 \\
  Babe Ruth   &714
\end{tabular}

The output will have two left-aligned columns with a vertical bar between them. This is specified in tabular’s argument {l|l}. Put the entries into different columns by separating them with an ampersand, &. The end of each row is marked with a double backslash, \\. Put a horizontal rule below a row, after a double backslash, with \hline. After the last row the \\ is optional, unless an \hline command follows to put a rule below the table.

The required and optional arguments to tabular consist of:

pos

Optional. Specifies the table’s vertical position. The default is to align the table so its vertical center matches the baseline of the surrounding text. There are two other possible alignments: t aligns the table so its top row matches the baseline of the surrounding text, and b aligns on the bottom row.

This only has an effect if there is other text. In the common case of a tabular alone in a center environment this option makes no difference.

cols

Required. Specifies the formatting of columns. It consists of a sequence of the following specifiers, corresponding to the types of column and intercolumn material.

l

A column of left-aligned items.

r

A column of right-aligned items.

c

A column of centered items.

|

A vertical line the full height and depth of the environment.

@{text or space}

Insert text or space at this location in every row. The text or space material is typeset in LR mode. This text is fragile (see \protect).

If between two columns there is no @-expression then LaTeX’s book, article, and report classes will put on either side of each column a space of length \tabcolsep, which by default is 6pt. That is, by default adjacent columns are separated by 12pt (so \tabcolsep is misleadingly named since it is only half of the separation between tabular columns). In addition, a space of 6pt also comes before the first column and after the final column, unless you put a @{...} or | there.

If you override the default and use an @-expression then LaTeX does not insert \tabcolsep so you must insert any desired space yourself, as in @{\hspace{1em}}.

An empty expression @{} will eliminate the space. In particular, sometimes you want to eliminate the space before the first column or after the last one, as in the example below where the tabular lines need to lie on the left margin.

\begin{flushleft}
  \begin{tabular}{@{}l}
    ...
  \end{tabular}
\end{flushleft}

The next example shows text, a decimal point between the columns, arranged so the numbers in the table are aligned on it.

\begin{tabular}{r@{$.$}l}
  $3$ &$14$  \\
  $9$ &$80665$
\end{tabular}

An \extracolsep{wd} command in an @-expression causes an extra space of width wd to appear to the left of all subsequent columns, until countermanded by another \extracolsep. Unlike ordinary intercolumn space, this extra space is not suppressed by an @-expression. An \extracolsep command can be used only in an @-expression in the cols argument. Below, LaTeX inserts the right amount of intercolumn space to make the entire table 4 inches wide.

\begin{tabular*}{4in}{l@{\extracolsep{\fill}}l}
  Seven times down, eight times up \ldots 
  &such is life!
\end{tabular*}

To insert commands that are automatically executed before a given column, load the array package and use the >{...} specifier.

p{wd}

Each item in the column is typeset in a parbox of width wd, as if it were the argument of a \parbox[t]{wd}{...} command.

A line break double backslash \\ may not appear in the item, except inside an environment like minipage, array, or tabular, or inside an explicit \parbox, or in the scope of a \centering, \raggedright, or \raggedleft declaration (when used in a p-column element these declarations must appear inside braces, as with {\centering .. \\ ..}). Otherwise LaTeX will misinterpret the double backslash as ending the row. Instead, to get a line break in there use \newline (see \newline).

*{num}{cols}

Equivalent to num copies of cols, where num is a positive integer and cols is a list of specifiers. Thus the specifier \begin{tabular}{|*{3}{l|r}|} is equivalent to the specifier \begin{tabular}{|l|rl|rl|r|}. Note that cols may contain another *-expression.

width

Required for tabular*, not allowed for tabular. Specifies the width of the tabular* environment. The space between columns should be rubber, as with @{\extracolsep{\fill}}, to allow the table to stretch or shrink to make the specified width, or else you are likely to get the Underfull \hbox (badness 10000) in alignment ... warning.

Parameters that control formatting:

\arrayrulewidth

A length that is the thickness of the rule created by |, \hline, and \vline in the tabular and array environments. The default is ‘.4pt’. Change it as in \setlength{\arrayrulewidth}{0.8pt}.

\arraystretch

A factor by which the spacing between rows in the tabular and array environments is multiplied. The default is ‘1’, for no scaling. Change it as \renewcommand{\arraystretch}{1.2}.

\doublerulesep

A length that is the distance between the vertical rules produced by the || specifier. The default is ‘2pt’.

\tabcolsep

A length that is half of the space between columns. The default is ‘6pt’. Change it with \setlength.

The following commands can be used inside the body of a tabular environment, the first two inside an entry and the second two between lines:

8.23.1 \multicolumn

Synopsis:

\multicolumn{numcols}{cols}{text}

Make an array or tabular entry that spans several columns. The first argument numcols gives the number of columns to span. The second argument cols specifies the formatting of the entry, with c for centered, l for flush left, or r for flush right. The third argument text gives the contents of that entry.

In this example, in the first row, the second and third columns are spanned by the single heading ‘Name’.

\begin{tabular}{lccl} 
  \textit{ID}       &\multicolumn{2}{c}{\textit{Name}} &\textit{Age} \\
  \hline  
  978-0-393-03701-2 &O'Brian &Patrick                  &55           \\
    ...
\end{tabular}

What counts as a column is: the column format specifier for the array or tabular environment is broken into parts, where each part (except the first) begins with l, c, r, or p. So from \begin{tabular}{|r|ccp{1.5in}|} the parts are |r|, c, c, and p{1.5in}|.

The cols argument overrides the array or tabular environment’s intercolumn area default adjoining this multicolumn entry. To affect that area, this argument can contain vertical bars | indicating the placement of vertical rules, and @{...} expressions. Thus if cols is ‘|c|’ then this multicolumn entry will be centered and a vertical rule will come in the intercolumn area before it and after it. This table details the exact behavior.

\begin{tabular}{|cc|c|c|}
  \multicolumn{1}{r}{w}       % entry one
    &\multicolumn{1}{|r|}{x}  % entry two 
    &\multicolumn{1}{|r}{y}   % entry three
    &z                        % entry four
\end{tabular}

Before the first entry the output will not have a vertical rule because the \multicolumn has the cols specifier ‘r’ with no initial vertical bar. Between entry one and entry two there will be a vertical rule; although the first cols does not have an ending vertical bar, the second cols does have a starting one. Between entry two and entry three there is a single vertical rule; despite that the cols in both of the surrounding multicolumn’s call for a vertical rule, you only get one rule. Between entry three and entry four there is no vertical rule; the default calls for one but the cols in the entry three \multicolumn leaves it out, and that takes precedence. Finally, following entry four there is a vertical rule because of the default.

The number of spanned columns numcols can be 1. Besides giving the ability to change the horizontal alignment, this also is useful to override for one row the tabular definition’s default intercolumn area specification, including the placement of vertical rules.

In the example below, in the tabular definition the first column is specified to default to left justified but in the first row the entry is centered with \multicolumn{1}{c}{\textsc{Period}}. Also in the first row, the second and third columns are spanned by a single entry with \multicolumn{2}{c}{\textsc{Span}}, overriding the specification to center those two columns on the page range en-dash.

\begin{tabular}{l|r@{--}l} 
  \multicolumn{1}{c}{\textsc{Period}}  
    &multicolumn{2}{c}{\textsc{Span}} \\ \hline
  Baroque          &1600           &1760         \\
  Classical        &1730           &1820         \\
  Romantic         &1780           &1910         \\
  Impressionistic  &1875           &1925
\end{tabular}

Although the tabular specification by default puts a vertical rule between the first and second columns, no such vertical rule appears in the first row here. That’s because there is no vertical bar in the cols part of the first row’s first \multicolumn command.

8.23.2 \vline

Draw a vertical line in a tabular or array environment extending the full height and depth of an entry’s row. Can also be used in an @-expression, although its synonym vertical bar | is more common. This command is rarely used in the body of a table; typically a table’s vertical lines are specified in tabular’s cols argument and overridden as needed with \multicolumn (see tabular).

The example below illustrates some pitfalls. In the first row’s second entry the \hfill moves the \vline to the left edge of the cell. But that is different than putting it halfway between the two columns, so between the first and second columns there are two vertical rules, with the one from the {c|cc} specifier coming before the one produced by the \vline\hfill. In contrast, the first row’s third entry shows the usual way to put a vertical bar between two columns. In the second row, the ghi is the widest entry in its column so in the \vline\hfill the \hfill has no effect and the vertical line in that entry appears immediately next to the g, with no whitespace.

\begin{tabular}{c|cc}
  x   &\vline\hfill y   &\multicolumn{1}{|r}{z} \\ % row 1  
  abc &def &\vline\hfill ghi                       % row 2  
\end{tabular}

8.23.3 \cline

Synopsis:

\cline{i-j}

In an array or tabular environment, draw a horizontal rule beginning in column i and ending in column j. The dash, -, must appear in the mandatory argument. To span a single column use the number twice, as with \cline{2-2}.

This example puts two horizontal lines between the first and second rows, one line in the first column only, and the other spanning the third and fourth columns. The two lines are side-by-side, at the same height.

\begin{tabular}{llrr} 
  a &b &c &d \\ \cline{1-1} \cline{3-4} 
  e &f &g &h 
\end{tabular}

8.23.4 \hline

Draw a horizontal line the width of the enclosing tabular or array environment. It’s most commonly used to draw a line at the top, bottom, and between the rows of a table.

In this example the top of the table has two horizontal rules, one above the other, that span both columns. The bottom of the table has a single rule spanning both columns. Because of the \hline, the tabular second row’s line ending double backslash \\ is required.

\begin{tabular}{ll} \hline\hline
  Baseball   &Red Sox  \\
  Basketball &Celtics  \\ \hline
\end{tabular}