- the standard unit in the International System of Units (SI) of dose equivalent having the same biological effect as one joule of x-rays per kilogram of recipient mass (or one gray): The average person receives about 2 to 3 one-thousandths of a sievert per year from naturally occurring radiation in the environment.Abbreviation: Sv
- the derived SI unit of dose equivalent, equal to 1 joule per kilogram. 1 sievert is equivalent to 100 rems
- (formerly) a unit of gamma radiation dose approximately equal to 8.4 × 10 –2 gray
