au revoir
Usage and formality
This phrase is versatile and can be used in almost any situation, from formal to informal. It is appropriate for friends, family, colleagues, and strangers. It is the default goodbye in most contexts.
Pronunciation
Pronounced 'oh ruh vwahr'. Note the silent 't' at the end of 'revoir'. The 'r' sound in French is often guttural or rolled, differing from the English 'r'.
Grammar
Literally, 'au' is a contraction of 'à le' (to the) and 'revoir' means 'seeing again'. It functions as a fixed expression.
Watch out
While 'au revoir' is very common, more informal goodbyes exist, such as 'salut' (used among close friends) or 'ciao' (borrowed from Italian). However, 'au revoir' is always a safe choice.
Notes
Au revoir: Standard goodbye, pronounced 'oh ruh vwahr'. Use in most situations.