Definition - What does Yuga mean?
Yuga is defined as an age or epoch by Hindu astronomy and cosmology. There are four distinct Yugas: Satya, Treta, Dvapara and Kali. As humankind passes through each of them, our collective righteousness, life span, wisdom and virtue diminishes until the world ends and is re-created.
It is believed that the world is currently in the Kali Yuga, which began in 3102 BCE, when Krishna left Earth. We will continue to be in this Yuga for many more years.
In the most decadent Yugas, spiritual knowledge and practices such as yoga become less important for most people, as they lose their connection to the spiritual side of their lives.
Yogapedia explains Yuga
Understanding which Yuga we are in and how each Yuga is different allows us to better understand the world around us and where we are heading. This makes it easier to face the physical and moral challenges of the current age. The Satya Yuga is a time of truth and righteousness, when humanity is governed by the gods and every action is driven by intrinsic goodness. This morality diminishes slightly in the Treta Yuga, as people become more materialistic and less focused on spirituality. During Dvapara Yuga, people desire achievement. They are pleasure-seeking and competitive, and their divine intellect disappears. Our current Yuga, the Kali Yuga, is a time of vice during which human existence is full of discord and strife.
By combining this knowledge of the Yugas and our current place in them with regular meditative yoga, we can become more at one with the universe and with ourselves. We may also begin to better understand the state of the world around us and accept it as part of a process of decay and rebirth. Practicing yoga and meditation allows us to stay grounded and in touch with the spiritual side of our lives during any Yuga.