In my opinion, it's much easy to see what is "alive" and what is not.
A "living" being is able to perform some kind of action by itself and independantly.
We know a tree is a living being because it grows, breathes, and procreates.
We know a bird is a living being because it can swing his wings to be able to fly, it's able to walk, it eats, breathes, procreates... etc.
In both cases it's all done independently and instinctively (bird).
We know a light bulb is not alive because if no one ever pulls the switch, or screw/unscrew it, it will always remain there in the same state as it was left untill it someday eventually gets decomposed. And even if some one pulls the switch on, what moves it's electric energy and photons. The bulb remains the same. It will be heated, but reamaining the same.
You can say "but its atoms will move on the process of decomposition and that may be a form of life".
I don't think an atom has life in itself. It has energy that simply makes the atom connect to another atom, or just be cast away from another atom, still having to connect to some other atom(s) in the end. They always do that.
This post bears a question I never gave much time to myself on answering it. I try to keep things simple. When I go off, I just go off. Pure lack of senses and thoughts. Pure hollow that I won't even feel. Much like a TV when it's set off.
Some people also believe that ghosts, spirits, demons, spectres, you name it, are all someone's life after death. But no one even knows what they are... they could even be a life form that have always existed and we take it as a supernatural matter. But the similarity of most of them (not all) to human beings is incredible and suspicious.