# How to renumber a property in a chapter, using lowercase letters instead of Numbers

I want to insert several new propositions in my second section,and name it 'Prop s','Prop t'...，I hope that anyone can help me :) Here is my code.

\documentclass{article}
\usepackage{amsthm}

\theoremstyle{definition}
\newtheorem{prop}{Prop}[section]

\begin{document}
\section{Intro}
\begin{prop}
First one.
\end{prop}
\section{Background}
\begin{prop}
Second one.
\end{prop}
\end{document}


## 1 Answer

The following example shows how to switch the environment's numbering system from 1.1, 1.2, etc to a, b, etc -- and also how revert to the initial numbering system.

\documentclass{article}
\usepackage{amsthm}
\theoremstyle{definition}
\newtheorem{prop}{Prop}[section]

\begin{document}
\section{Intro}
\begin{prop} First one. \end{prop}

\section{Background}
\let\origprop\theprop  % save the current style
\renewcommand\theprop{\alph{prop}} % change style
\setcounter{prop}{18} % just for this example
\begin{prop} Second one. \end{prop}
\begin{prop} Third one. \end{prop}
\begin{prop} Fourth one. \end{prop}

\section{Analysis}
\renewcommand\theprop{\origprop} % revert to orig. style
\begin{prop} Fifth one. \end{prop}

\end{document}

• Exactly what I was looking after! Thanks a lot. – user8281063 Feb 26 at 11:32