In geometry, a side is a straight line that is part of a shape. A shape made of straight lines is called a polygon. The number of sides on a polygon can be written as ${\displaystyle n}$.

A side can also mean the face of a 3D shape. A 3D shape made of flat faces is called a polyhedron. The number of faces on a polyhedron can be written as ${\displaystyle F}$.^[1][2][3]

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