trial period vs period of time

trial period and period of time both are nouns.

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

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

Other hypernyms of trial period include period, time period.

trial period (noun)	period of time (noun)
a period of time during which someone or something is tested	an amount of time