lifetime

noun

1. the time that the life of someone or something continues; the term of a life: peace within our lifetime.
2. Physics. mean life.

adjective

3. for the duration of a person’s life: He has a lifetime membership in the organization.

noun

1. 1. the length of time a person or animal is alive
   2. (as modifier)a lifetime supply
2. the length of time that something functions, is useful, etc
3. physics the average time of existence of an unstable or reactive entity, such as a nucleus, excited state, elementary particle, etc; mean life

n.also life-time, early 13c., from life (n.) + time (n.). One word from 19c. Old English had lifdæg in same sense, literally “life day.” n.

1. The period of time during which an individual is alive.
2. The period of time during which property, an object, a process, or a phenomenon exists or functions.