short bone vs os

short bone and os both are nouns.

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

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

short bone: a bone that is of approximately equal dimension in all directions
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of short bone include bone.

short bone (noun)	os (noun)
a bone that is of approximately equal dimension in all directions	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening