I. ˈ ̷ ̷ˌ ̷ ̷ noun
Etymology: Middle English liftime, from lif life + time — more at life , time
1. : the time that a life continues : the duration of the existence of a living being or a thing
a lifetime of writing nonfiction — Stuart Chase
these edifices … possess only a limited lifetime — Osbert Sitwell
during its lifetime the university has absorbed several other institutions — American Guide Series: Maryland
2.
a. : the duration of the existence of an ion or subatomic particle
b. : half-life
II. adjective
Etymology: lifetime , noun
1. : lifelong
a lifetime love affair with books
2. : of long duration or continuance
lifetime legislation
3. : measured or achieved over the span of a career
a baseball player's lifetime batting average