radian

American  

[rey-dee-uhn] / ˈreɪ di ən /

noun

Mathematics.

1. the measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958°. rad

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radian British  

/ ˈreɪdɪən /

noun

1.  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

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radian Scientific  

/ 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″.

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Etymology

Origin of radian

First recorded in 1875–80; radi(us) + -an

Example Sentences

He was diagnosed with radial tunnel syndrome and underwent a procedure to decompress the radian nerve in his right arm that July.

From Los Angeles Times

A representative of the former star of “Glee” said Saturday that Reich, president of clothing company AYR, proposed with a 4-carat elongated radian cut ring that he personally helped design.

From Washington Times

One big thing tau fixes is radian angles.

From The Verge

You mention the regrettable practice of referring to torque units in joules per radian.

From Nature

For example, radians could be made a new SI unit, and the unit 1 could be formally coupled with notation that includes the type of quantity that it represents.

From Nature