Fait accompli

Around 45% of English vocabulary is of French origin, most coming from the Anglo-Norman spoken by the upper classes in England for several hundred years after the Norman Conquest, before the language settled into what became Modern English. Thoroughly English words of French origin, such as art, competition, force, machine, money, police, publicity, role, routine and table, are pronounced according to English rules of phonology, rather than French, and are commonly used by English speakers without any consciousness of their French origin.

This article, on the other hand, covers French words and phrases that have entered the English lexicon without ever losing their character as Gallicisms: they remain unmistakably "French" to an English speaker. They are most common in written English, where they retain French diacritics and are usually printed in italics. In spoken English, at least some attempt is generally made to pronounce them as they would sound in French; an entirely English pronunciation is regarded as a solecism.

Some of them were never "good French", in the sense of being grammatical, idiomatic French usage. Some others were once normal French but have become very old-fashioned, or have acquired different meanings and connotations in the original language, to the extent that they would not be understood (either at all, or in the intended sense) by a native French speaker.

c'est la guerre: "That's war!", or...

c'est la vie: "That's life!" or "Such is life!"

Through the evolution of the language, many words and phrases are no longer used in modern French. Also there are expressions that, even though grammatically correct, do not have the same meaning in French as the English words derived from them. Some older word usages still appear in Quebec French.

...
Wikipedia