shoulder blade vs os

shoulder blade and os both are nouns.

Word	Noun	Adjective	Verb	Adverb
shoulder blade	Yes	No	No	No
os	Yes	No	No	No

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

shoulder blade: either of two flat triangular bones one on each side of the shoulder in human beings
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of shoulder blade include bone.

shoulder blade (noun)	os (noun)
either of two flat triangular bones one on each side of the shoulder in human beings	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening