This is one of the most difficult questions upon which scientists and philosophers are baffling even today.

If you ask me, life is just a happening in the universe, like a play. We call this leela in Sanskrit. We are all part of this play - a momentary happening in the largest stage called universe, playing our own unique characters. Our only goal should be to perform well sensibly by giving our best, irrespective of the situations happen to us from outside.

Biologically, a life is simply the one which is aware of its existence. Everything is present including inert elements, rocks, mountains, and even space for that matter in this universe. But insects, plants, animals ,humans and probably aliens (if they are somewhere) - all these are aware that they are alive. So we call this as life.

At a basic level, how we know something as living is through the presence of the twin instincts of survival and reproduction. So anything capable of protecting itself and reproducing itself can be said to be living - whether it be humans, animals, plants or micro organisms.

At a deeper level, how we know something as living is based on how we relate to life itself. If we are sensitive to what's around us, we can find a living quality in not just what's considered living organisms but all of nature itself - the flowing rivers and the vast oceans, the majestic mountains, the active volcanoes, the howling wind and the space that carries it all.