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[stuh-rey-dee-uh n] /stəˈreɪ di ən/
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.
Abbreviation: sr.
Origin of steradian
First recorded in 1880-85; ste(reo)- + radian Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for steradian


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 sr
Word Origin
C19: from stereo- + radian
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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steradian in Science
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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