Bonne nuit !

It is pronounced approximately bun nwee.

More precisely:

• bonne sounds like bon in French, with a nasal vowel: /bɔn/
• nuit is /nɥi/, which can be tricky for English speakers

A simple learner-friendly approximation is:

• bonne = bun
• nuit = something like nwee

The t in nuit is silent.

Bonne is the feminine form of bon, which means good.

In French, adjectives must agree with the noun they describe:

• bon = masculine singular
• bonne = feminine singular

Since nuit is a feminine noun, French uses:

• bonne nuit

not:

• bon nuit

Nuit is feminine.

That is why you say:

• une nuit
• la nuit
• bonne nuit

This is something learners simply need to memorize with the noun.

This is one of the most common questions.

• Bonsoir ! means good evening and is used as a greeting when you meet someone in the evening.
• Bonne nuit ! means good night and is usually used when someone is leaving to go to bed, or when you are saying goodbye for the night.

So:

• If you arrive at a dinner party in the evening, say Bonsoir !
• If you are leaving and going home to sleep, say Bonne nuit !

French does not usually use Bonne nuit ! as an evening greeting.

You usually say Bonne nuit ! when the night is ending for that person in a social sense—especially when they are going to sleep, going home late, or ending the day.

For example, you can say it:

• to a child before bed
• to a friend leaving late at night
• to family members before going to sleep

It signals the end of the evening/night, not just the time of day.

It works in both formal and informal situations.

You can say Bonne nuit ! to:

• friends
• family
• coworkers
• strangers

It is neutral and polite. The form does not change depending on tu or vous.

No. Bonne nuit ! by itself is completely natural and very common.

A longer version such as:

• Je te souhaite une bonne nuit
• Je vous souhaite une bonne nuit

is grammatically correct, but much less common in everyday speech. Most people simply say:

• Bonne nuit !

In Bonne nuit !, French is using a fixed expression, similar to other short wishes.

Compare:

• Bonne journée ! = Have a good day
• Bonne soirée ! = Have a good evening
• Bonne nuit ! = Good night

In these expressions, French normally does not use an article. So Bonne nuit ! is the standard form, not Une bonne nuit !

Yes. Bonne nuit ! can be said to:

• one person
• several people

The expression itself does not change.

For example:

• to one person: Bonne nuit !
• to a group: Bonne nuit !

French does not need a different form here.

Yes. Some common ones are:

• Bonne nuit, dors bien ! = Good night, sleep well!
• Bonne nuit à tous ! = Good night, everyone!
• Très bonne nuit ! = Have a very good night
• Fais de beaux rêves ! = Sweet dreams / Have nice dreams

But the basic and most useful expression is simply:

• Bonne nuit !