\documentclass{article} \usepackage[version=3]{acro} \DeclareAcroEnding{possessive}{'s}{'s} \NewAcroCommand\acg{m}{\acropossessive\UseAcroTemplate{first}{#1}} \NewAcroCommand\acsg{m}{\acropossessive\UseAcroTemplate{short}{#1}} \NewAcroCommand\aclg{m}{\acropossessive\UseAcroTemplate{long}{#1}} \NewAcroCommand\acfg{m}{% \acrofull \acropossessive \UseAcroTemplate{first}{#1}% } \NewAcroCommand\iacsg{m}{% \acroindefinite \acropossessive \UseAcroTemplate{short}{#1}% } \DeclareAcronym{MP}{ short = MP , long = Member of Parliament , long-plural-form = Members of Parliament , long-possessive-form = Member's of Parliament } \begin{document} \acg{MP} \par \acsg{MP} \par \aclg{MP} \par \acfg{MP} \par \iacsg{MP} \par \end{document}