arm bone vs humerus

arm bone and humerus both are nouns.

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

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

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

arm bone (noun)	humerus (noun)
a bone in the arm	bone extending from the shoulder to the elbow