When you sleep (unless you're a horse), your body is horizontal:

Which way is vertical and horizontal. Which way is vertical horizontal? Which way is vertical and horizontal? Which way is vertical horizontal?

The terms vertical and horizontal often describe directions: Horizontal lines go side to side and have a slope of 0; Horizontal vs vertical horizontal refers to physical space from left to right, or space that is parallel to the horizon.

Vertical refers to space from up to down that is perpendicular to. In astronomy, geography, and related sciences and contexts, a direction or plane passing by a given point is said to be vertical if it contains the local gravity direction at that. Vertical lines go up and down and have a slope that is undefined;

A vertical line is perpendicular to a horizontal line. The opposite of vertical, something horizontal is arranged sideways, like a person lying down. It is a straight line which goes from top to bottom and bottom to top.

A vertical line goes up and down, and a horizontal line goes across. The terms vertical and horizontal often describe directions: Vertical is up and down, and horizontal is left to right.