coccyx vs os

coccyx and os both are nouns.

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

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

Other hypernyms of coccyx include bone.

coccyx (noun)	os (noun)
the end of the vertebral column in humans and tailless apes	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening