life vs period of time

life and period of time both are nouns.

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

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

life: the period during which something is functional (as between birth and death)
period of time: an amount of time

Other hypernyms of life include period, time period.

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

Other hypernyms of life include period, time period.

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

Other hypernyms of life include period, time period.

life (noun)	period of time (noun)
living things collectively	an amount of time
animation and energy in action or expression
the experience of being alive; the course of human events and activities
an account of the series of events making up a person's life
a motive for living
a living person
the organic phenomenon that distinguishes living organisms from nonliving ones
the condition of living or the state of being alive
a characteristic state or mode of living
the course of existence of an individual; the actions and events that occur in living
the period during which something is functional (as between birth and death)
the period between birth and the present time
the period from the present until death
a prison term lasting as long as the prisoner lives