ethmoid bone vs os

ethmoid bone and os both are nouns.

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

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

ethmoid bone: one of the eight bones of the cranium; a small bone filled with air spaces that forms part of the eye sockets and the nasal cavity
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of ethmoid bone include bone.

ethmoid bone (noun)	os (noun)
one of the eight bones of the cranium; a small bone filled with air spaces that forms part of the eye sockets and the nasal cavity	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening