1 Definition
The surroundings or social setting in which a person lives, works, or moves, including its people, customs, and atmosphere.
2 In Use
After years in the quiet countryside, she found the fast-talking milieu of the city newsroom thrilling and a little bewildering.
3 Word Origin
mi + lieu O.Fr. · middle, place → milieu 19th c. English
Milieu began in French as a plain description of position: the middle place, a point halfway between two others. Over time the French used it for the space in which something sits, and then for the surrounding conditions that act on a person or thing. English borrowed it in the 1800s with its French spelling and sound intact, and it settled into use as a graceful way to name the whole atmosphere of a social world.
💡Fun Fact
The second half of milieu, lieu, appears in another everyday phrase: in lieu of, meaning in place of something. It also hides inside lieutenant, which literally means one who holds the place of a superior. English even gives milieu two accepted plurals, milieus and milieux, so you can pick the one that feels more at home in your sentence. That makes it a small reminder of how many ordinary English words are quietly French places in disguise.