amsthm with \usepackage[french]{babel}

Question

When I use amsthm with \usepackage[french]{babel}, I got Proof becoming Démonstration. In general, it is good, but in a special case of mine, I need it to be Proof. Could you help me to get this?

\documentclass[a4paper]{article}

\usepackage{amsthm}

\usepackage[utf8]{inputenc}     %% format d'encodage
\usepackage[french]{babel}      %% typographie française

\newtheorem{thm}{Theorem}

\begin{document}

\begin{thm}
This is a great theorem.
\end{thm}

\begin{proof}
This is a simple proof.
\end{proof}

\end{document}

Answer 1

You can use the optional argument for proof to provide the required name:

\documentclass[a4paper]{article}

\usepackage{amsthm}

\usepackage[utf8]{inputenc}     %% format d'encodage
\usepackage[french]{babel}      %% typographie française

\newtheorem{thm}{Theorem}

\begin{document}

\begin{thm}
This is a great theorem.
\end{thm}

\begin{proof}[Proof]
This is a simple proof.
\end{proof}

\end{document}

If you need to change the name for all the proof environments you can use

\addto\captionsfrench{\renewcommand\proofname{Proof}}

A complete example:

\documentclass[a4paper]{article}
\usepackage{amsthm}

\usepackage[utf8]{inputenc}     %% format d'encodage
\usepackage[french]{babel}      %% typographie française

\newtheorem{thm}{Theorem}
\addto\captionsfrench{\renewcommand\proofname{Proof}}

\begin{document}

\begin{thm}
This is a great theorem.
\end{thm}

\begin{proof}
This is a simple proof.
\end{proof}

\end{document}