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Noun: rad  rad
  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 Système International d'Unités; equal to the angle at the centre of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees)
    - radian

Derived forms: rads

Type of: angular unit, radioactivity unit

Encyclopedia: Rad