occiput vs os

occiput and os both are nouns.

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

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

Other hypernyms of occiput include bone.

occiput (noun)	os (noun)
back part of the head or skull	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening