Radiation Dosage

The total amount of radiation energy absorbed by a substance. This value is usually expressed in "ergs per gram", and is denoted by the following units:
Roentgen - a quantity of gamma or X-Ray radiation equal to approximately 83 ergs of absorbed energy per gram of air;
REP (Roentgen Equivalent - Physical) - a quantity of ionization that causes an energy absorption of approximately 83 to 93 ergs per gram of tissue;
REM (Roentgen Equivalent - Man) - similar to REP, except used to denote biological effects; and;
RAD - the unit of dosage related to elastomers, independent of type of radiation specimen, and denoting energy absorption level of 100 ergs per gram of elastomer: approximately equal to 1.2 Roentgens.