carpal bone vs os

carpal bone and os both are nouns.

Word	Noun	Adjective	Verb	Adverb
carpal bone	Yes	No	No	No
os	Yes	No	No	No

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

Other hypernyms of carpal bone include bone.

carpal bone (noun)	os (noun)
any of the eight small bones of the wrist of primates	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening