the unit of plane angle adopted under the Systeme International d'Unites; equal to the angle at the center of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees)
例句
用作名词 (n.)
A unit of angular distance equals to one thousandth of a radian. 一种角距离单位相当于弧度的千分之一。
美
['reɪdiən]
