bellybutton vs navel

bellybutton and navel both are nouns.

Word	Noun	Adjective	Verb	Adverb
bellybutton	Yes	No	No	No
navel	Yes	No	No	No

As nouns, bellybutton and navel are synonyms defined as:

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

bellybutton (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