rad /ˈræd/
  弧度單位
  Rad obs. imp. & p. p. of Read, Rede.
  ◄ ►
  rad
       n 1: a unit of absorbed ionizing radiation equal to 100 ergs per
            gram of irradiated material
       2: 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) [syn: radian]