He was watching TV all day.

He is looking outside from the window now.

The crescent moon is floating in the sky, it's very beautiful.

There is a beautiful park in Mikazuki City.

The moon on the second day of the lunar calendar is floating in the sky, and it's very beautiful.

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.