Definitions
from The American Heritage® Dictionary of the English Language, 4th Edition
 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, approximately 57°17ʹ44.6〞. See Table at measurement.
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. In the International System of Units, the derived unit of plane angular measure of angle equal to the angle subtended at the centre of a circle by an arc of its circumference equal in length to the radius of the circle. Symbol: rad
from the GNU version of the Collaborative International Dictionary of English
 n. An arc of a circle which is equal to the radius, or the angle measured by such an arc.
from The Century Dictionary and Cyclopedia
 n. The angle subtended at the center of a circle by an are equal in length to the radius. Also called the unit angle in circular measure. It is equal to 57° 17′ 44″. 80625 nearly.
 n. A unit of angular velocity equivalent, approximately, to 0.15916 revolutions per second, or, strictly, to revolutions per second: in full, radian per second.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
 n. the unit of plane angle adopted under the Systeme International d'Unites; equal to the angle at the center of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees)
Etymologies
from The American Heritage® Dictionary of the English Language, 4th Edition
from Wiktionary, Creative Commons Attribution/ShareAlike License
Examples

Light en  ergy gathered by the sheaths was relayed by lines called radian draws.

A radian is a measurement used to describe angles.

A radian is the equivalent of (a) 2 angular degrees (b) 1/(2) of the angle comprising a full circle (c) the circumference of a unit circle (d) 1 = 4 of the angle comprising a full circle

When to use "radian" mode in casio scientific calculator fx85ms.? what is difference between methematics and logic or arthematics? true/false For any two subsets A, B in a vector space [A intersection B] = [A] intersection

One radian of phase, symbolized rad (although you can write out the whole word '' radian ''), is equal to about

Your symplectic one, though, if it has made an error of one A.U. in its position, will put it one radian ahead or behind in its orbit, but still in its correct orbit.

You'd have to have a pretty accurate launcher radian to assure the launch elevation was precisely the same as last time.

As a result, the radian/degree error was quickly diagnosed and known long before any potential use of these results for policy purposes.

Re #19C: I had nothing to do with the radian/degree thing, although they all pretend that.

Spanner Frew yelled something down to one of the Rovers amidships, and the crewman waved back, moving to tighten a radian draw.
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