Usage on farewell remark

Question

I found several forms of farewell remarks like these:

Goodbye
Good-bye
Good-by
Bye
Bye-Bye

Are these remarks equivalent in both written and spoken English ?

Answer 1

More or less, they're all equivalent. Let's break it down for each version:

Goodbye

This is the most standard/conventional, and a perfectly formal version.

Good-bye

A more old-fashioned version of goodbye, also acceptable, though less standard.

Good-by

Alternative (rather less common) spelling of good-bye.

Bye

A shortened version of goodbye; perfectly acceptable, though slightly less formal.

Bye-Bye

Means the same thing; the least formal of all versions, rather colloquial.