"rad" . "The radian is a unit of angle defined as the angle subtended at the center of a circle by an arc that is equal in length to the radius of the circle."@en . "radian"@en . . . "radiaal"@nl . . "\u5F27\u5EA6"@zh . "The radian is a unit of angle defined as the angle subtended at the center of a circle by an arc that is equal in length to the radius of the circle. The radian is a derived unit in the International System of Units." . .