Gray (Gy)

The gray (symbol: Gy) is the derived SI unit of absorbed dose, defined as the absorption of one joule of ionizing radiation energy per kilogram of matter. Expressed in SI base units, one gray equals one meter squared per second squared. Adopted by the 15th General Conference on Weights and Measures (CGPM) in 1975, the gray was named in honor of British physicist Louis Harold Gray, a pioneer in radiobiology, officially superseding the non-SI rad unit.