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radian

[rey-dee-uh n]
noun Mathematics.
  1. the measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958°. Abbreviation: rad

Origin of radian

First recorded in 1875–80; radi(us) + -an
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for radian

Historical Examples of radian

British Dictionary definitions for radian

radian

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 angleSymbol: rad

Word Origin for radian

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.

Online Etymology Dictionary, © 2010 Douglas Harper
radian in Medicine

radian

[rā′dē-ən]
n.
  1. 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.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
radian in Science

radian

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