Naraka (Sanskrit: नरक; Pali: निरय Niraya) is a term in Buddhist cosmology usually referred to in English as "hell" (or "hell realm") or "purgatory". The Narakas of Buddhism are closely related to diyu, the hell in Chinese mythology. A Naraka differs from the hell of Christianity in two respects: firstly, beings are not sent to Naraka as the result of a divine judgment or punishment; and secondly, the length of a being's stay in a Naraka is not eternal, though it is usually incomprehensibly long, from hundreds of millions to sextillions (1021) of years.
A being is born into a Naraka as a direct result of its accumulated actions (karma) and resides there for a finite period of time until that karma has achieved its full result. After its karma is used up, it will be reborn in one of the higher worlds as the result of karma that had not yet ripened.
Physically, Narakas are thought of as a series of cavernous layers which extend below Jambudvīpa (the ordinary human world) into the earth. There are several schemes for enumerating these Narakas and describing their torments. The Abhidharma-kosa (Treasure House of Higher Knowledge) is the root text that describes the most common scheme, as the Eight Cold Narakas and Eight Hot Narakas.
Each lifetime in these Narakas is twenty times the length of the one before it.
Each lifetime in these Narakas is eight times the length of the one before it.
Some sources describe five hundred or even hundreds of thousands of different Narakas.
The sufferings of the dwellers in Naraka often resemble those of the Pretas, and the two types of being are easily confused. The simplest distinction is that beings in Naraka are confined to their subterranean world, while the Pretas are free to move about.
There are also isolated and boundary hells called Pratyeka Narakas (Pali: Pacceka-niraya) and Lokantarikas.佛告比丘：「此四天下有八千天下圍遶其外。復有大海水周匝圍遶八千天下。復有大金剛山遶大海水。金剛山外復有第二大金剛山。二山中間窈窈冥冥。日月神天有大威力。不能以光照及於彼。彼有八大地獄。其一地獄有十六小地獄。第一大地獄名想。第二名黑繩。第三名堆壓。第四名叫喚。第五名大叫喚。第六名燒炙。第七名大燒炙。第八名無間。其想地獄有十六小獄。小獄縱廣五百由旬。第一小獄名曰黑沙。二名沸屎。三名五百丁。四名飢。五名渴。六名一銅釜。七名多銅釜。八名石磨。九名膿血。十名量火。十一名灰河。十二名鐵丸。十三名釿斧。十四名犲狼。十五名劍樹。十六名寒氷。
The Buddha told the bhikṣus, "There are 8,000 continents surrounding the four continents [on earth]. There is, moreover, a great sea surrounding those 8,000 continents. There is, moreover, a great diamond mountain range encircling that great sea. Beyond this great diamond mountain range is yet another great diamond mountain range. And between the two mountain ranges lies darkness. The sun and moon in the divine sky with their great power are unable to reach that [darkness] with their light. In [that space between the two diamond mountain ranges] there are eight major hells. Along with each major hell are sixteen smaller hells.
"The first major hell is called Thoughts. The second is called Black Rope. The third is called Crushing. The fourth is called Moaning. The fifth is called Great Moaning. The sixth is called Burning. The seventh is called Great Burning. The eighth is called Unremitting. The Hell of Thoughts contains sixteen smaller hells. The smaller hells are 500 square yojana in area. The first small hell is called Black Sand. The second hell is called Boiling Excrement. The third is called Five Hundred Nails. The fourth is called Hunger. The fifth is called Thirst. The sixth is called Single Copper Cauldron. The seventh is called Many Copper Cauldrons. The eighth is called Stone Pestle. The ninth is called Pus and Blood. The tenth is called Measuring Fire. The eleventh is called Ash River. The twelfth is called Iron Pellets. The thirteenth is called Axes and Hatchets. The fourteenth is called Jackals and Wolves. The fifteenth is called Sword Cuts. The sixteenth is called Cold and Ice.""
Descriptions of the Narakas are a common subject in some forms of Buddhist commentary and popular literature as cautionary tales against the fate that befalls evildoers and an encouragement to virtue.
The Mahāyāna Sūtra of the bodhisattva Kṣitigarbha (Dìzàng or Jizō) graphically describes the sufferings in Naraka and explains how ordinary people can transfer merit in order to relieve the sufferings of the beings there.
Chinese Buddhist texts considerably enlarged upon the description of Naraka (Diyu), detailing additional Narakas and their punishments, and expanding the role of Yama and his helpers, Ox-Head and Horse-Face. In these texts, Naraka became an integral part of the otherworldly bureaucracy which mirrored the imperial Chinese administration.