noun
• geometry
a unit of measurement of angles.
"a full rotation around the circle is 2π radians."

## Description

Radians are a unit that measure rotation as the ratio of arc length over the radius of a circle. For example, an angle can be measured using radians by dividing the corresponding arc length by its radius.

In the radian angle system, a full rotation is equal to (tau) radians, where is approximately equal to and is defined as the circumfence of any circle divided by its radius. A half rotation is equal to (pi) radians, where is approximately equal to and is defined as the circumference of any circle divided by its diameter. Read more…

## Related Terms

An angle is a measure of rotation or turning and is usually measured in degrees or radians. In geometry, an angle is the figure formed by two rays, sharing a common endpoint called the vertex.

A circle is a basic shape used throughout mathematics. A circle is defined as a shape where every point along its perimeter is an equal distance from its center.

Degrees are a unit of measurement for angles, representing the rotation between two rays. The degree angle system divides a full rotation into 360 units called degrees.