arm bone vs os longum

arm bone and os longum both are nouns.

Word	Noun	Adjective	Verb	Adverb
arm bone	Yes	No	No	No
os longum	Yes	No	No	No

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

arm bone: a bone in the arm
os longum: in limbs of vertebrate animals: a long cylindrical bone that contains marrow

Other hypernyms of arm bone include long bone.

arm bone (noun)	os longum (noun)
a bone in the arm	in limbs of vertebrate animals: a long cylindrical bone that contains marrow