radian

radian

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

Origin:
1875–80; radi(us) + -an

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World English Dictionary
radian (ˈreɪdɪən)
 
n
rad 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 angle
 
[C19: from radius]

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Medical Dictionary

radian ra·di·an (rā'dē-ən)
n.
Abbr. rad
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.
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American Heritage
Science Dictionary
radian   (rā'dē-ən)  Pronunciation Key 
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 © 2002. Published by Houghton Mifflin. All rights reserved.
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