Niraya: lit. 'the downward-Path', the nether or infernal world, usually translated by 'hell', is one of the 4 lower courses of existence apāya. The Buddhists are well aware that on account of the universal sway of impermanence a life in hell, just as in heaven, cannot last eternally, but will after exhaustion of the kamma which has caused the respective form of rebirth, necessarily be followed again by a new death and a new rebirth, according to the stored-up kamma.
See also: Buddhist cosmology
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.