sphenoid vs os

sphenoid and os both are nouns.

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

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

Other hypernyms of sphenoid include bone.

sphenoid (noun)	os (noun)
butterfly-shaped bone at the base of the skull	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening