Formal:
* Fermez la bouche. (fer-may la boosh) - This is the most direct and literal translation, meaning "Close the mouth."
* Veuillez fermer la bouche. (vuh-lay fer-may la boosh) - This is a more polite way to say it, meaning "Please close your mouth."
Informal:
* Ferme ta gueule. (ferm ta gûl) - This is very informal and slangy, meaning "Shut your mouth." It's considered rude and should only be used with close friends.
* Tais-toi. (tay-twah) - This is also informal, meaning "Be quiet" or "Shut up." It's a bit more neutral than "Ferme ta gueule" but still not appropriate for formal settings.
Other options:
* Tu peux fermer la bouche ? (too puh fer-may la boosh) - This is a polite way to ask someone to close their mouth, meaning "Can you close your mouth?"
* Ne parle pas avec la bouche pleine. (nuh parl pah ah-vehk la boosh plenn) - This means "Don't talk with your mouth full," and it's a polite way to tell someone to close their mouth when they are eating.
The best option will depend on the specific situation and the relationship between the speaker and the listener.