light beam vs moon-ray

light beam and moon-ray both are nouns.

Word	Noun	Adjective	Verb	Adverb
light beam	Yes	No	No	No
moon-ray	Yes	No	No	No

As nouns, moon-ray is a hyponym of light beam; that is, moon-ray is a word with a more specific, narrower meaning than light beam:

Other hyponyms of light beam include heat ray, high beam, moon ray, moonbeam, sunbeam, sunray, laser beam, low beam.

light beam (noun)	moon-ray (noun)
a column of light (as from a beacon)	a ray of moonlight