Yuga

Webster's Dictionary

(n.) Any one of the four ages, Krita, or Satya, Treta, Dwapara, and Kali, into which the Hindoos divide the duration or existence of the world.

The Nuttall Encyclopedia

A name given by the Hindus to the four ages of the world, and, according to M. Barth, of the gradual triumph of evil, as well as of the successive creations and destructions of the universe, following each other in the lapse of immense periods of time.