One of the two units used to measure the amount of radiation absorbed by an object or person, known as the absorbed doses which reflects the amount of energy that radioactive sources (with any type of ionising radiation) deposit in materials (e.g., water, tissue, air) through which they pass. One grey (Gy) is the international system of units (SI) equivalent of 100 rads, which is equal to an absorbed dose of 1 Joule/kilogram. An absorbed dose of 0. 01 Gy means that 1 gramme of material absorbed 100 ergs of energy (a small but measurable amount) as a result of exposure to radiation. For additional information, see Doses in Our Daily Lives and Measuring Radiation.