bare bone vs os

bare bone and os both are nouns.

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

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

Other hypernyms of bare bone include bone.

bare bone (noun)	os (noun)
bone stripped of flesh	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening