steradian

[stuh-rey-dee-uhn]

Phonetic (Standard)IPA

noun

Geometry.

a solid angle at the center of a sphere subtending a section on the surface equal in area to the square of the radius of the sphere. sr

steradian

/ ��əˈ��ɪ��ɪə�� /

noun

sr.��an SI unit of solid angle; the angle that, having its vertex in the centre of a sphere, cuts off an area of the surface of the sphere equal to the square of the length of the radius

steradian

A unitless measure of solid angles. A solid angle projecting from the center of a sphere and cutting its surface has a measure of s/r² steradians, where s is the surface area of the sphere cut out by the solid angle, and r is the radius of the sphere.
See also radian

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Word History and Origins

Origin of steradian¹

First recorded in 1880–85; ste(reo)- + radian

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Word History and Origins

Origin of steradian¹

C19: from _stereo- + _radian

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Example Sentences

Examples have not been reviewed.

For the record, the amount of extra light they found bouncing around the universe is about 10 nanowatts per square meter per steradian, a measure of solid angle on the sky.

From

-ster stercoraceous

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