hour vs period of time

hour and period of time both are nouns.

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

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

Other hypernyms of hour include period, time period.

hour (noun)	period of time (noun)
distance measured by the time taken to cover it	an amount of time
a period of time equal to 1/24th of a day
clock time
a special and memorable period