Mizu is my best friend.

In the old days, people used to draw water directly from the river and drink it.

Please give me a glass of water.

He drank water.

He grew up in a colony in Africa.

The air in this room is fresh.

What will you use this empty box for?

Looking at the bird flying high in the sky, I felt freedom.

The altitude of this airplane is 10,000 meters.

In mathematics, an empty set refers to a set that does not contain any elements.