nap vs beauty sleep

nap and beauty sleep both are nouns.

Word	Noun	Adjective	Verb	Adverb
nap	Yes	No	Yes	No
beauty sleep	Yes	No	No	No

As nouns, beauty sleep is a hyponym of nap; that is, beauty sleep is a word with a more specific, narrower meaning than nap:

Other hyponyms of nap include kip.

nap (noun)	beauty sleep (noun)
sleeping for a short period of time (usually not in bed)	sleep before midnight
a card game similar to whist; usually played for stakes
the yarn (as in a rug or velvet or corduroy) that stands up from the weave
a soft or fuzzy surface texture
a period of time spent sleeping

nap (verb)	beauty sleep (verb)
take a siesta