os longum vs long bone

os longum and long bone both are nouns.

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

As nouns, os longum and long bone are synonyms defined as:

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

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