arcus zygomaticus vs os

arcus zygomaticus and os both are nouns.

Word	Noun	Adjective	Verb	Adverb
arcus zygomaticus	Yes	No	No	No
os	Yes	No	No	No

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

arcus zygomaticus: the slender arch formed by the temporal process of the cheekbone that bridges to the zygomatic process of the temporal bone
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of arcus zygomaticus include bone.

arcus zygomaticus (noun)	os (noun)
the slender arch formed by the temporal process of the cheekbone that bridges to the zygomatic process of the temporal bone	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening