marrowbone vs os

marrowbone and os both are nouns.

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

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

marrowbone: a bone containing edible marrow; used especially in flavoring soup
os: rigid connective tissue that makes up the skeleton of vertebrates

Other hypernyms of marrowbone include bone.

marrowbone (noun)	os (noun)
a bone containing edible marrow; used especially in flavoring soup	rigid connective tissue that makes up the skeleton of vertebrates
	a mouth or mouthlike opening