hyoid bone vs os

hyoid bone and os both are nouns.

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

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

hyoid bone: 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 bone include bone.

hyoid bone (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