radian

[rey-dee-uh n]

noun Mathematics.

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. 2019

Examples from the Web for radian

Historical Examples of radian

Strob, strob, n. the angular velocity of one radian per second.
Chambers's Twentieth Century Dictionary (part 4 of 4: S-Z and supplements)
Various

British Dictionary definitions for radian

radian

noun

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

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

radian in Medicine

radian

[rā′dē-ən]

n.

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.

radian in Science

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″.