protrusion vs caput

protrusion and caput both are nouns.

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

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

protrusion: something that bulges out or is protuberant or projects from its surroundings
caput: a headlike protuberance on an organ or structure

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

protrusion (noun)	caput (noun)
the act of projecting out from something	the upper part of the human body or the front part of the body in animals; contains the face and brains
something that bulges out or is protuberant or projects from its surroundings	a headlike protuberance on an organ or structure