Formal:
* Au revoir: This is the most common and formal way to say goodbye. It literally means "until we see each other again."
* Bonne journée: This means "have a good day" and is a polite way to say goodbye during the day.
* Bonne soirée: This means "have a good evening" and is a polite way to say goodbye in the evening.
Informal:
* Salut: This is a casual way to say goodbye, similar to "hi" in English.
* Ciao: This is an Italian word that has been adopted into French and is also used informally.
* A plus tard: This means "see you later" and is a casual way to say goodbye when you expect to see the person again soon.
* Bisous: This is a casual way to say goodbye that literally means "kisses." It is often used between friends and family.
The best way to choose the right phrase depends on your relationship with the person you are saying goodbye to.