the measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958°. Abbreviation: rad
Origin of radian
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for radian
Historical Examples of radian
Strob, strob, n. the angular velocity of one radian per second.
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
"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
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.
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.