Side

A square with four sides

In geometry, a side is a line that is part of a flat figure made from straight lines. It is also a face in a solid three-dimensional object. The number of sides in a polygon is often written as $n$, while the number of faces in a polyhedron is often written as $F$.

As an example, the square on the right has four sides. The sides in this picture are made with black straight lines. The four sides are:

1. the black straight line from A to B
2. the black straight line from B to C
3. the black straight line from C to D
4. the black straight line from D to A

Other uses

• A side may also mean a part of something. For example, on a human body, the right side means the parts of the body that make up the right half of the body.
• Inside and outside are terms use to show where something is. If something is inside, it is in something. For example, the sentence "The cookies are inside of the container." means that the cookies are in the container. The area within the canister is the inside of the canister. The outside is the area not in the canister. Outside is the opposite of inside.

Related pages

• Area