How to change from "CHAPITRE" to "CHAPTER"

Question

I am writing a PhD thesis. Some parts of my thesis need to be in French, but the main language is English. I am using

\documentclass[english,letterpaper,12pt,oneside,final]{book}

\usepackage[french, english, USenglish]{babel}

Here is my problem:

\chapter{...} is generating CHAPITRE, which I do not want and it is happening because of the "french" option. But I want CHAPTER as the heading instead of CHAPITRE.

Answer 1

Let's see what happens.

1. You have english as a global option;

2. You repeat it in the options to babel.

3. When babel is loaded, the english global option is passed first, then french; when it comes to english, it does nothing, because the relevant .ldf file has already been loaded; the same holds for USenglish.

However, babel sets as main language the one specified in the last loaded language definition file, which in this case is french.ldf.

Solution: don't specify english in the global options, so

\documentclass[letterpaper,12pt,oneside,final]{book}

Alternatively, if you really need the global option, call babel as

\usepackage[french,main=english]{babel}