collarbone vs os

collarbone and os both are nouns.

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

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

Other hypernyms of collarbone include bone.

collarbone (noun)	os (noun)
bone linking the scapula and sternum	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening