lifetime

noun

Etymology: From Middle English lyftyme, equivalent to life + time. Cognate with Icelandic líftími (“lifetime”). Compare also Saterland Frisian Lieuwendstied, Dutch leeftijd and levenstijd, German Low German Levenstied, German Lebenszeit, Danish livstid, Swedish livstid.

1. The duration of the life of someone or something.

   “a project that will take many human lifetimes to complete”

   “the operational lifetime of an aircraft component”

2. A long period of time.

   “I've been waiting a lifetime for a train.”