modiolus vs os

modiolus and os both are nouns.

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

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

Other hypernyms of modiolus include bone.

modiolus (noun)	os (noun)
the central conical bony pillar of the cochlea	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening