The Power of Good-Bye was created on 1998-09-22.

good bye or bye

Good-bye is more formal than bye-bye. Bye-bye, now.

bye bye and good bye are the same thing except that you are putting good in front of it

Good bye is more formal, used with those people with whom you may not be familiar - it is more polite. Bye Bye is fine for friends, neighbours and relations, in other words, an informal good bye

Aurevoir.

A bientôt.

But if you say "good bye" or "bye bye" everyone understands you.