tarsal bone vs os

tarsal bone and os both are nouns.

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

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

Other hypernyms of tarsal bone include bone.

tarsal bone (noun)	os (noun)
any bone of the tarsus	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening