nap vs period of time

nap and period of time both are nouns.

Word	Noun	Adjective	Verb	Adverb
nap	Yes	No	Yes	No
period of time	Yes	No	No	No

As nouns, period of time is a hypernym of nap; that is, period of time is a word with a broader meaning than nap:

Other hypernyms of nap include period, time period.

nap (noun)	period of time (noun)
sleeping for a short period of time (usually not in bed)	an amount of time
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)	period of time (verb)
take a siesta