round bone vs bone

round bone and bone both are nouns.

Word	Noun	Adjective	Verb	Adverb
round bone	Yes	No	No	No
bone	Yes	Yes	Yes	No

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

Other hypernyms of round bone include os.

round bone (noun)	bone (noun)
bones that are round in shape	a shade of white the color of bleached bones
	rigid connective tissue that makes up the skeleton of vertebrates
	the porous calcified substance from which bones are made

round bone (adjective)	bone (adjective)
	consisting of or made up of bone

round bone (verb)	bone (verb)
	remove the bones from
	study intensively, as before an exam