Measurement Units Standards & Services Department

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Supplementary Units Definition

Unit	Symbol	measurand	Definition
The radian	rad	Plane Angle	The radian is the plane angle between two radii of a circle which cut off on the circumference an are equal in length to the radius
The steradian	sr	Solid Angle	The steradian is the solid angle which having its vertex in the center of sphere, cuts off an area of the surface of sphere equal to that of a square with its sids of equal length to this radius of the sphere.