# radian

[rey-dee-uh n]

- the measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958°. Abbreviation: rad

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## Origin of radian^{}

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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

## Examples from the Web for radian

### Historical Examples

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

## radian

- 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 angleSymbol: rad

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## Word Origin

C19: from radius

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

## Word Origin and History for radian

### n.

"angle subtended at the center of a circle by an arc equal in length to the radius," 1879, from radius.

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Online Etymology Dictionary, © 2010 Douglas Harper

## radian

(rā′dē-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.

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The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

## radian

[rā′dē-ən]

- 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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The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.