nap vs drowse

nap and drowse both are nouns.

Word	Noun	Adjective	Verb	Adverb
nap	Yes	No	Yes	No
drowse	Yes	No	Yes	No

As verbs, drowse is a hyponym of nap; that is, drowse is a word with a more specific, narrower meaning than nap:

Other hyponyms of nap include doze, snooze.

nap (noun)	drowse (noun)
sleeping for a short period of time (usually not in bed)	a light fitful sleep
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)	drowse (verb)
take a siesta	be on the verge of sleeping
	sleep lightly or for a short period of time