radian

[ rey-dee-uhn ]

noun

, Mathematics.

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

radian

/ ˈreɪdɪən /

noun

1. 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 rad

radian

/ 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″.

Word History and Origins

Origin of radian¹

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

Word History and Origins

Origin of radian¹

C19: from radius

Example Sentences

Strob, strob, n. the angular velocity of one radian per second.

From Project Gutenberg

The torsion couple per radian was determined by preliminary experiments.

From Project Gutenberg