- rad - a unit of absorbed ionizing radiation equal to 100 ergs per gram of irradiated material
--1 is a kind of radioactivity unit
- radian, rad - 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)
--2 is a kind of angular unit
--2 has parts: milliradian - radian, rad - 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)