protrusion vs belly

protrusion and belly both are nouns.

Word	Noun	Adjective	Verb	Adverb
protrusion	Yes	No	No	No
belly	Yes	No	Yes	No

As nouns, belly is a hyponym of protrusion; that is, belly is a word with a more specific, narrower meaning than protrusion:

protrusion: something that bulges out or is protuberant or projects from its surroundings
belly: a part that bulges deeply

Other hyponyms of protrusion include frontal eminence, occipital protuberance, caput, mogul, nub, nubble, snag, wart.

protrusion (noun)	belly (noun)
the act of projecting out from something	the underpart of the body of certain vertebrates such as snakes or fish
something that bulges out or is protuberant or projects from its surroundings	the region of the body of a vertebrate between the thorax and the pelvis
	a protruding abdomen
	the hollow inside of something
	a part that bulges deeply

protrusion (verb)	belly (verb)
	swell out or bulge out