lunula vs half-moon

lunula and half-moon both are nouns.

Word	Noun	Adjective	Verb	Adverb
lunula	Yes	No	No	No
half-moon	Yes	No	No	No

As nouns, lunula and half-moon are synonyms defined as:

lunula and half-moon: the crescent-shaped area at the base of the human fingernail

Other synonyms of lunula include lunule.

lunula (noun)	half-moon (noun)
a crescent-shaped metal ornament of the Bronze Age	the crescent-shaped area at the base of the human fingernail
the crescent-shaped area at the base of the human fingernail	the time at which the Moon is at first or last quarter when half its face is illuminated