"Absorbed dose is a measure of the energy deposited in a medium by ionising radiation. It is equal to the energy deposited per unit mass of a medium, and so has the unit joules (J) per kilogram (kg), with the adopted name of gray (Gy) where 1 Gy = 1 J.kg-1."
"absorbed dose rate (Gy.s-1): amount of radiation delivered over a time period"
"rad: the international unit of absorbed dose pre-1980 where 1 Gy = 100 rad"