Life.

Life is like beauty- it is in the eye of the beholder.

Life is also like obscenity you will know it when you see it.

Most scientific definitions of biological life include the ability to metabolize matter to energy, the ability to grow, the ability to reproduce, the ability to respond to stimuli. From that definition, fire is alive. Fire breaks down combustible materials, it grows and spreads, and can send sparks out making new fires. Fire responds to wind, water, and to Firemen.

So, to specifically eliminate fire, the concept of cellular structure is added. That then eliminates viruses and prions as being alive.

To include Artificial Intelligence as being alive, some include self-awareness as a criteria; but that excludes almost all plants and animals.

I'd say life takes action. Life is that which is dependent on its environment but also changes the environment around it to make it more suitable for it. The first single-celled organisms processed our primitive atmosphere, filling it with carbon dioxide. Then plants evolved, and changed the carbon dioxide to oxygen. Then animals evolved, to process oxygen and create carbon dioxide, and hopefully maintain a balance.

Life altered the atmosphere, and the Earth, to make it suited for life.