There is only relative definations in the world.
Nothing is what it is, by itself.

There is light, only if there is darkness
There is joy, only if there is pain
There is relief, only if there is stress
There is wisdom, only if there is stupidity

You are a girl. only when there is a boy
You have long hair, only when there is someone with short hair.
You are human, only when there is non-humans.
You are alive, only when there is something dead.

This is a vegetable, only when there is meat
This is a shirt, only when there is pants
This is a friend, only when there is enemies
This is a smile, only when there is a tear.

You only know yourself, when you have known others.
You are only YOU, when there are others.

Know that through this, you are knowing something else.

-Rong