Bonne soirée !

Because soirée is a feminine noun in French. Adjectives usually agree with the noun they describe, so:

• bon = masculine singular
• bonne = feminine singular

Since it is une soirée, you say Bonne soirée !

Soirée means evening, but in this kind of expression it refers to the time someone is about to spend. French often uses expressions like this to wish someone a good period of time:

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

So soirée is the noun being described by bonne.

This is one of the most common questions.

• Bonsoir ! is usually a greeting used when meeting someone in the evening, like Good evening
• Bonne soirée ! is usually said when leaving, like Have a nice evening

So:

• You arrive at 7 p.m. → Bonsoir !
• You leave at 9 p.m. → Bonne soirée !

Sometimes people may use them a little flexibly, but that is the main difference.

Usually, no. It normally sounds like a farewell, not a greeting.

If you are arriving somewhere in the evening, say:

• Bonsoir !

If you are leaving and want to wish the other person a pleasant evening, say:

• Bonne soirée !

A simple approximate pronunciation for English speakers is:

• bonne ≈ bun
• soirée ≈ swah-ray

Very roughly together: bun swah-ray

A few pronunciation notes:

• The o in bonne is not like English bone
• The r in soirée is the French r
• The final -ée sounds like ay

No. In bonne, the final -ne is part of the feminine spelling, but the word is pronounced as one syllable, approximately bun.

That said, the spelling matters because it shows feminine agreement with soirée.

It works in both formal and informal situations. You can say it to:

• friends
• coworkers
• shop staff
• neighbors
• strangers

It is a very normal, polite everyday expression.

If you want to make it more formal or warmer, you can add something:

• Je vous souhaite une bonne soirée. = I wish you a pleasant evening.
• Très bonne soirée ! = Have a very nice evening!

Normally, no. In this kind of fixed wish, French usually leaves out the article.

So you say:

• Bonne soirée !
• not usually Une bonne soirée !

This is similar to other common expressions:

• Bon courage !
• Bonne chance !
• Bon voyage !

They are used at different times and in different situations.

• Bonne soirée ! = said earlier, when the evening is still ahead of the person
• Bonne nuit ! = said later, when the person is going to bed or ending the night

For example:

• Leaving a dinner at 8:30 p.m. → Bonne soirée !
• Saying goodbye to someone who is going to sleep → Bonne nuit !

So Bonne nuit ! is not just another version of Bonne soirée !

Yes. Some common variations are:

• Très bonne soirée ! = Have a very nice evening!
• Bonne fin de soirée ! = Enjoy the rest of your evening
• Passez une bonne soirée ! = Have a nice evening
• Passe une bonne soirée ! = same, informal singular

These all sound natural, but Bonne soirée ! is already perfectly standard on its own.

No. It is very common in writing because this is a friendly wish:

• Bonne soirée !

But without it, the phrase is still correct:

• Bonne soirée.

In texts, emails, and messages, both are possible. The exclamation mark just makes it feel a little more warm or lively.