Formal:
* Nuitée: This is the most literal translation, meaning "night stay" or "overnight stay." It's more formal and commonly used for things like hotel stays.
Informal:
* Pyjama party: This is a more informal and common term, especially for children's sleepovers. It translates directly to "pajama party."
* Soirée pyjama: Similar to "pyjama party," this means "pajama evening" and is another informal option.
* Dormir chez un ami: This literally translates to "sleep at a friend's house" and is a good option if you want to be more specific about the activity.
Other options:
* Passer la nuit chez quelqu'un: This means "spend the night at someone's place."
* Faire une nuit blanche: This means "pull an all-nighter" and might be used if the sleepover involves staying up late.
The best way to choose the right translation depends on the context and the formality of the situation.