\documentclass[french,12pt,fleqn,a4paper,twoside,openright]{book}
\newcommand{\chaptertoc}[1]{\chapter*{#1}
\addcontentsline{toc}{chapter}{#1}
\markboth{{#1}}{{#1}}}
% Set the beginning of a LaTeX document
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{rotating}
\usepackage{lscape}
\usepackage{amsthm}
\usepackage{makeidx} % allows for indexgeneration
\usepackage[-20pt]{extsizes}
\usepackage{geometry}
\geometry{lmargin=3.2cm,vmargin=4.6cm, rmargin=3.2cm}
\usepackage[T1]{fontenc}
\usepackage{fmtcount}\usepackage{textcomp}
\usepackage[headsepline]{scrpage2}
\pagestyle{scrheadings}
\clearscrheadfoot
\usepackage{txfonts} \usepackage{algorithm,algorithmic}
\newcommand{\lesss}{\rotatebox[origin=c]{90}{$\land$}}
\newcommand{\less}{\ \lesss\ }
\usepackage[toc,page]{appendix}
\usepackage{multirow}
\usepackage{minitoc}
\usepackage{caption}
\hyphenation{prépos-si-tions}
\renewcommand{\&}{et}
\usepackage[super]{nth}
%\usepackage{Packages/phs_goodies}
\usepackage{graphicx}
\usepackage{slashbox}
\usepackage{amsmath}
\usepackage{epsfig}
\usepackage{epstopdf}
%\usepackage{xcolor,colortbl}
\usepackage{subfig}
\usepackage{fancyhdr}
\usepackage{multirow}
\usepackage{algorithm}
\usepackage{algorithmic}
\usepackage[french]{babel}
\addto\captionsfrench{\def\tablename{Tableau}} % à activer pour version française
\usepackage[utf8]{inputenc}
\usepackage{enumitem}
I write this sentence in french
Barker and Cornacchia ont proposé le système \textit{B} \& \textit{C}
But it display
Barker and Cornacchia ont proposé le système B et C
i.e., the "&" is replaced by "et". Why
\documentclass{...}and ending with\end{document}. – Phelype Oleinik Mar 10 '18 at 15:43\renewcommand{\&}{et}what is this doing in your document? – Johannes_B Mar 10 '18 at 15:50epsfig– David Carlisle Mar 10 '18 at 16:11epsfig\ has been obsolete for more than 20 years. It is simply replaced withgraphicx. Thefrenchoption ofbabelis already loaded with the document class (that's the right place).txfontsshould be replaced withnewtxtextandnewtxmath,slashboxwithdiagbox. As to hyphenation, prépossitions are not prépositions… – Bernard Mar 10 '18 at 16:16etisandin French.&is generally pronouncedand– User Mar 10 '18 at 22:59