In Hindu mythology, the term "Yuga" refers to the distinct eras in the cyclical concept of time. There are four Yugas: Satyuga (the age of truth and righteousness), Treta Yuga (characterized by virtue but declining morals), Dvapara Yuga (where righteousness diminishes), and Kali Yuga (the age of darkness and ignorance). Each Yuga signifies different spiritual and moral conditions, with humanity's condition deteriorating over time. The cyclical nature of Yugas reflects the belief in rebirth and the eventual return to a state of balance and harmony in the universe.