Survivors of the atomic bombings of Hiroshima and Nagasaki, their children and grandchildren are referred to in Japanese as hibakusha, literally "explosion-affectedpeople." According to the Atomic Bomb Survivors Relief Law in Japan, there are certain recognized categories of hibakusha: people exposed directly to the nuclear bombings; people exposed within a 2-km radius of the hypocenter within two weeks of the explosion; people exposed to radioactive fallout generally; and those exposed in utero.

However, the term hibakusha has recently also been taken to apply to people anywhere in the world who have been exposed to radiation. Its common usage has spread to encompass any person exposed to radiation from the nuclear fuel chain, through the use and production of nuclear weapons, especially through nuclear weapons tests, as well as the processes that create and produce nuclear energy.