arm bone vs elbow bone

arm bone and elbow bone both are nouns.

Word	Noun	Adjective	Verb	Adverb
arm bone	Yes	No	No	No
elbow bone	Yes	No	No	No

As nouns, elbow bone is a hyponym of arm bone; that is, elbow bone is a word with a more specific, narrower meaning than arm bone:

Other hyponyms of arm bone include humerus, radius, ulna.

arm bone (noun)	elbow bone (noun)
a bone in the arm	the inner and longer of the two bones of the human forearm