Identity of life

What is life? People have asked me this and I have asked this question to people and myself a million times. All of us turn to something and say "Thats not life" or say "thats life". We dont like our jobs so say "Thats not life". We travel by bus in the scorching heat and look at the person in the air conditioned car crossing us and say "Thats life!" But what is life?Do we understand it?
I have read many sayings and forwards talking about what life is and is not etc. But that does not define life and give it an identity.It only tells you all that life comprises of. So why cant we define life?
Because unfortunately the entire irony of life is that you understand its meaning when you see death.. We all live life every moment, every single day and seem to have understood one more day of life not because we lived one more day of life but because we are one more day closer to death. It is the presence of black that makes white what it is. It is the realisation of darkness that makes sunlight what it is. In the absence of one, the other is incomplete. In the absence of death there is no meaning of life. Thus life itself derives its identity from death. It is the absence of death that creates life and not vice versa. Thus we got to understand death to understand life!!