hyoid vs os

hyoid and os both are nouns.

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

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

hyoid: a U-shaped bone at the base of the tongue that supports the tongue muscles
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of hyoid include bone.

hyoid (noun)	os (noun)
a U-shaped bone at the base of the tongue that supports the tongue muscles	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening

hyoid (adjective)	os (adjective)
of or relating to the hyoid bone