Existance. Any organism which exhibits respiration, reproduction, growth, and movement. Colloquial: to 'have a life'; to posses some semblence of a regular social interaction timetable. Lifespan; the span of time which someone spends on the planet.

The above is, as far as we are concerned, totally unproven and there is merely circumstantial evidence to suggest it's existance. We all know that it's science fiction and that the only true existance is in cyberspace.