Kalpa

Kalpa [Skt.] (Wyl. bskal pa) - an aeon, a vast period of time related to the different phases of a great universe (or trichiliocosm), according to Abhidharma literature.

A great kalpa (Skt. mahakalpa; Wyl. bskal chen) is the period of time during which the universe passes through the four periods (or medium kalpas) of

1. formation (Wyl. chags pa'i bskal pa),
2. duration (Wyl. gnas pa'i bskal pa),
3. destruction (Wyl. 'jig pa'i bskalpa) and
4. voidness (Wyl. stong pa'i bskalpa).

Each of these four periods is made up of twenty intermediate kalpas, which are also sometimes subdivided into periods of increase and decrease (of the merit and life-span of beings living during that period).