kalpa of decline ［壊劫］ ( e-kō): One of the four kalpas. The period in which a world collapses. The third period of the four-stage cycle of formation, continuance, decline, and disintegration, which a world is said to undergo repeatedly. The time it takes to complete this four-kalpa cycle is called a major kalpa. The kalpa of decline, like the other three kalpas of the cycle, lasts for twenty small kalpas. Each small kalpa is said to last nearly sixteen million years. In the first nineteen small kalpas of the kalpa of decline, sentient beings in the six lower worlds from hell through the world of heavenly beings gradually disappear. In the last small kalpa, the world is destroyed by the three greater calamities caused by water, fire, and wind. See also kalpa.