# What Is a Right Angle?

## What Is a Right Angle?

A right angle is an angle of 90°.

A right angle is a quarter of a revolution.

**Note**: Right angles are often denoted by adding a small right angle that forms a square with the angle.

### Dictionary Definition

The Oxford English Dictionary defines a right angle as "an angle of ninety degrees; specifically one formed by two perpendicular lines, as in the corner of a square."

## Real Examples of Right Angles

The angles below are all right angles:

## A Real Example of a Right Angle: The Right Triangle

A right triangle is a triangle containing a right angle.

The right triangle is one of the most useful triangles in mathematics.

It is used for Pythagoras' theorem and in trigonometry.