Some French words and expressions commonly used in English:
Bon appétit good appetite
English equivalent is “Enjoy your meal.”
Bon voyage good trip
English has “Have a good trip”, but Bon voyage is more elegant.
C’est la vie that’s life
Same meaning and usage in both languages
Au contraire on the contrary
Usually used playfully in English.
Chic sounds more chic than “stylish.”
Also: Plus ça change