umbilicus vs bellybutton

umbilicus and bellybutton both are nouns.

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

As nouns, umbilicus and bellybutton are synonyms defined as:

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

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