os lunatum vs semilunar bone

os lunatum and semilunar bone both are nouns.

Word	Noun	Adjective	Verb	Adverb
os lunatum	Yes	No	No	No
semilunar bone	Yes	No	No	No

As nouns, os lunatum and semilunar bone are synonyms defined as:

Other synonyms of os lunatum include lunate bone.

os lunatum (noun)	semilunar bone (noun)
one of the eight small wrist bones	one of the eight small wrist bones