noun Download 🔗Share 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 Examples : "The angle formed when you wrap the radius of a circle around its edge is one radian, a common unit for measuring angles in math and physics. " math technical science Chat with AIVocabulary GamePractice Reading