calcaneus vs os

calcaneus and os both are nouns.

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

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

Other hypernyms of calcaneus include bone.

calcaneus (noun)	os (noun)
the largest tarsal bone; forms the human heel	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening