vertebra vs os

vertebra and os both are nouns.

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

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

Other hypernyms of vertebra include bone.

vertebra (noun)	os (noun)
one of the bony segments of the spinal column	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening