# Radian meaning

rādē-ən
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".
(geometry) In the International System of Units, the derived unit of plane angular measure of angle equal to the angle subtended at the centre of a circle by an arc of its circumference equal in length to the radius of the circle. Symbol: rad.
noun
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
From the Latin radius. A unit of plane angular measurement equivalent to the angle between two radii that enclose a section of a circle's circumference (arc) equal in length to the length of a radius.There are 2 radians in a circle. See also frequency and radius.
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## Origin of radian

• radi(us) –an

### From American Heritage Dictionary of the English Language, 5th Edition

• From radi(us) + -an