belly button vs umbilicus

belly button and umbilicus both are nouns.

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

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

belly button and umbilicus: a scar where the umbilical cord was attached

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

belly button (noun)	umbilicus (noun)
a scar where the umbilical cord was attached	a scar where the umbilical cord was attached