umbilicus vs belly button

umbilicus and belly button both are nouns.

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

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

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

Other synonyms of umbilicus include bellybutton, navel, omphalos, omphalus.

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