# Radian meaning

A unit of angular measure equal to the angle subtended at the center of a circle by an arc equal in length to the radius of the circle, approximately 57°17'44.6".

noun

A supplementary unit of the International System used in angular measure. One radian is equal to the angle subtended at the center of a circle by an arc equal in length to the radius of the circle, approximately 57°17'44.6".

The basic unit of plane angle in the SI system, equal to 57° 17′ 44.8″ (57.29578°, the angle formed at the center of a circle by two radii cutting off an arc whose length is equal to the radius of the circle): one degree equals 0.017454 radian and 360 degrees equals 2π radians.

noun

## Origin of radian

**radi(us)****–an**### From American Heritage Dictionary of the English Language, 5th Edition

- From radi(us) + -an
### From Wiktionary