My humblest apologies for the lateness of this reply.
Now, Life is the condition that defines all beings that are alive. Anything alive can grow, reproduce and self sustain themselves through processes of transforming matter into energy from which they draw their sustenance. This is the concept of life in the organic, Real Life sense of the word. In narutoverse, however, this pertains only to half of the equation. While is true that plants and other non sentient animals are alive and fill the above definition, humans and sentient animals have another concept linked to their life: Soul or Spirit. Ninjas and sentient beings in narutoverse are only alive if they have both a functioning physical, organic body and a functioning spiritual entity or soul. Both linked together make for the condition of being alive.
Now, just one more before we get into the technique (really, I'm sorry for how much this is stretching out, but we have to go over this and it's more beneficial if you at least give an attempt to answer than for me to just give you everything): how would you define the Spirit or Soul? This question is moreso based in the Naruto Universe than in ours, but if you want to try and touch on ours I won't stop you (as long as you include what it is in Narutoverse).