kneecap vs os sesamoideum

kneecap and os sesamoideum both are nouns.

Word	Noun	Adjective	Verb	Adverb
kneecap	Yes	No	Yes	No
os sesamoideum	Yes	No	No	No

As nouns, os sesamoideum is a hypernym of kneecap; that is, os sesamoideum is a word with a broader meaning than kneecap:

kneecap: a small flat triangular bone in front of the knee that protects the knee joint
os sesamoideum: any of several small round bones formed in a tendon where it passes over a joint

Other hypernyms of kneecap include sesamoid, sesamoid bone.

kneecap (noun)	os sesamoideum (noun)
a small flat triangular bone in front of the knee that protects the knee joint	any of several small round bones formed in a tendon where it passes over a joint

kneecap (verb)	os sesamoideum (verb)
shoot in the kneecap, often done by terrorist groups as a warning