Definition of "yuga"

yuga

noun
plural yugas
1. (Hinduism) In Hindu theology, a period of a few hundred or thousand years, or an epoch or era within a cycle of four ages: the Satya Yuga (or Krita Yuga), the Dvapara Yuga, the Treta Yuga and finally the Kali Yuga, with lengths ranging from 432,000 to 1,728,000 years.
  Quotations
  To Biardeau the linear nature of the declining dharma and the cyclical nature of the yugas make an unhappy marriage, and she ultimately rejects the idea of a true correspondence or rapport between the appearance of Vișņu as avatāra and the yuga cycle.
  1991, Deborah A. Soifer, The Myths of Narasimha and Vamana: Two Avatars in Cosmological Perspective, page 147
  There is, you will note, a pattern of decreased duration in the yugas. Moving from the Krta Yuga, the yuga closest to primordial perfection, each progressive yuga grows shorter and shorter, as chaos and decrepitude increase in prominence.
  1998, Sean M. O'Shea, Meryl A. Walker, The Millennium Myth: The Ever-Ending Story, page 39
  To explain further, there are four ages or millenniums called yugas. The duration of Satya-yuga is 1,728,000 years. The duration of Treta-yuga is 1,296,000 years. The duration of Dvapara-yuga is 864,000 years. The duration of Kali-yuga, the present age, is 432,000 years, and began around 5,000 years ago. These four yugas make one cycle, and one thousand cycles equal one day of Brahma, after which there is a partial annihilation of the universe during Brahma's night. Lord Brahma lives for 100 years, 360 days in each year.
  2005, Stephen Knapp, The Heart of Hinduism: The Eastern Path to Freedom, Empowerment and Illumination, pages 386, 489