duration vs period of time

duration and period of time both are nouns.

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

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

Other hypernyms of duration include period, time period.

duration (noun)	period of time (noun)
continuance in time	an amount of time
the property of enduring or continuing in time
the period of time during which something continues