belly button vs navel

belly button and navel both are nouns.

Word	Noun	Adjective	Verb	Adverb
belly button	Yes	No	No	No
navel	Yes	No	No	No

As nouns, belly button and navel are synonyms defined as:

Other synonyms of belly button include bellybutton, omphalos, omphalus, umbilicus.

belly button (noun)	navel (noun)
a scar where the umbilical cord was attached	a scar where the umbilical cord was attached
	the center point or middle of something