Radian

n. central angle of an arc of any circle that is equal in length to the radius of the same circle (Mathematics)

The radian, in mathematics, is a unit of plane angle, equal to 180/π degrees, or about 57.2958 degrees. It is represented by the symbol "rad" or, more rarely, by the superscript c (for "circular measure"). For example, an angle of 1.2 radians would be written as "1.2 rad" or "1.2c" (the second symbol can be mistaken for a degree: "1.2°").
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Noun
1. the unit of plane angle adopted under the Systeme International d'Unites; equal to the angle at the center of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees)
(synonym) rad
(hypernym) angular unit
(part-meronym) milliradian

n. radian, central angle of an arc of any circle that is equal in length to the radius of the same circle (Mathematics)

n. radian, central angle of an arc of any circle that is equal in length to the radius of the same circle (Mathematics)

v. ray, radiate