All living things start from one cell. As these cells multiply (we will talk more about cells in the next part) they form the living thing. And, as the cells form the living thing, that thing eventually becomes a distinguishable, visible object. Basically, it finally becomes a baby tiger cub and is born.
Then, as the baby cubs grows to seek, obtain and use energy it begins to grow. Based off its amount of energy it can obtain, the cub will grow and be very productive. This thing grows because cells reproduce. Without the steady reproduction of muscle cells, bone cells, etc. the cub wouldn’t grow.
With non-living things, this is not the case. Although non-living things can appear to be growing (like a river flood, clouds getting bigger, etc.) they do not grow in the same sense as living things. Just like the reproduction thing. Non-living things can reproduce but not nearly in the same way as living things, this separates them.
Thus, non-living things cannot grow in the same sense as living things and thus it can be reserved for living things alone.