diaphysis vs os longum

diaphysis and os longum both are nouns.

Word	Noun	Adjective	Verb	Adverb
diaphysis	Yes	No	No	No
os longum	Yes	No	No	No

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

diaphysis: the main (mid) section of a long bone
os longum: in limbs of vertebrate animals: a long cylindrical bone that contains marrow

Other hypernyms of diaphysis include long bone.

diaphysis (noun)	os longum (noun)
the main (mid) section of a long bone	in limbs of vertebrate animals: a long cylindrical bone that contains marrow