The Gray unit (symbol: Gy) is a measure of absorbed radiation dose in a material, particularly in biological tissues. It quantifies the amount of energy deposited by ionizing radiation, such as X-rays or gamma rays, per kilogram of matter. One Gray is equivalent to one joule of radiation energy absorbed per kilogram. The Gray unit is commonly used in fields like radiation therapy and radiology to assess the effectiveness of treatments and the potential risks of exposure. Understanding the Gray unit helps medical professionals ensure safe and effective radiation use in diagnosing and treating diseases, particularly cancer.