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radian

[ rey-dee-uhn ]

noun

, Mathematics.
  1. the measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958°. : rad


radian

/ ˈreɪdɪən /

noun

  1. an SI unit of plane angle; the angle between two radii of a circle that cut off on the circumference an arc equal in length to the radius. 1 radian is equivalent to 57.296 degrees and π/2 radians equals a right angle rad
“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


radian

/ dē-ən /

  1. 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″.


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Word History and Origins

Origin of radian1

First recorded in 1875–80; radi(us) + -an
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Word History and Origins

Origin of radian1

C19: from radius
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Example Sentences

Strob, strob, n. the angular velocity of one radian per second.

The torsion couple per radian was determined by preliminary experiments.

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radial velocityradiance