astragalus vs os

astragalus and os both are nouns.

Word	Noun	Adjective	Verb	Adverb
astragalus	Yes	No	No	No
os	Yes	No	No	No

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

astragalus: the bone in the ankle that articulates with the leg bones to form the ankle joint
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of astragalus include bone.

astragalus (noun)	os (noun)
the bone in the ankle that articulates with the leg bones to form the ankle joint	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening