ALL meanings of radian
ra·di·an
R r - noun radian A unit of angle, equal to an angle at the center of a circle whose arc is equal in length to the radius. 1
- noun radian the measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958°. Abbreviation: rad. 1
- noun radian an SI unit of plane angle; the angle between two radii of a circle that cut off on the circumference an arc equal in length to the radius. 1 radian is equivalent to 57.296 degrees and π/2 radians equals a right angle 0
- noun radian 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 0
- noun radian The radian is the plane angle between two radii of a circle that cut off on the circumference an arc equal in length to the radius. 0