Real Dictionary

bye
convention: Bye and bye-bye are informal ways of saying goodbye.

bye in American English
of secondary importance
something incidental or secondary

bye in American English 1
noun: in a tournament, the preferential status of a player or team not paired with a competitor in an early round and thus automatically advanced to play in the next round

bye in American English 2
interjection

bye in British English 1
noun: the situation in which a player or team in an eliminatory contest wins a preliminary round by virtue of having no opponent

bye in British English 2
sentence substitute: goodbye

bye- in American English
prefix

goodbye in British English 2
noun: a leave-taking; parting
sentence substitute: farewell: a conventional expression used at leave-taking or parting with people and at the loss or rejection of things or ideas