1. the branch of theology that is concerned with such final things as death and Last Judgment; Heaven and Hell; the ultimate destiny of humankind

From Wikipedia Eschatology concerns expectations of the end of the present age, human history, or of the world itself. The end of the world or end times is predicted by several world religions, which teach that negative world events will reach a climax. Belief that the end of the world is imminent is known as apocalypticism, and over time has been held both by members of mainstream religions and by doomsday cults. In the context of mysticism, the term refers metaphorically to the end of ordinary reality and to reunion with the divine. Various religions treat eschatology as a future event prophesied in sacred texts or in folklore.

The Abrahamic religions maintain a linear cosmology, with end-time scenarios containing themes of transformation and redemption. In later Judaism, the term "end of days" makes reference to the Messianic Age and includes an in-gathering of the exiled Jewish diaspora, the coming of the Messiah, the resurrection of the righteous, and the world to come. Some forms of Christianity depict the end time as a period of tribulation that precedes the second coming of Christ, who will face the rise of the Antichrist along with his power structure and false prophets, and usher in the Kingdom of God. In Islam, the Day of Judgment is preceded by the appearance of the Masīḥ ad-Dajjāl, and followed by the descending of ʿĪsā (Jesus), which shall triumph over the false Messiah or Antichrist; his defeat will lead to a sequence of events that will end with the sun rising from the west and the beginning of the Qiyāmah (Judgment Day).

Dharmic religions tend to have more cyclical worldviews, with end-time eschatologies characterized by decay, redemption, and rebirth (though some believe transitions between cycles are relatively uneventful). In Hinduism, the end time occurs when Kalki, the final incarnation of Vishnu, descends atop a white horse and brings an end to the current Kali Yuga, completing a cycle that starts again with the regeneration of the world. In Buddhism, the Buddha predicted his teachings would be forgotten after 5,000 years, followed by turmoil. It says a bodhisattva named Maitreya will appear and rediscover the teachings of the Buddha Dharma, and that the ultimate destruction of the world will then come through seven suns.

Since the development of the concept of deep time in the 18th century and the calculation of the estimated age of planet Earth, scientific discourse about end times has considered the ultimate fate of the universe. Theories have included the Big Rip, Big Crunch, Big Bounce, and Big Freeze (heat death). Social and scientific commentators also worry about global catastrophic risks and scenarios that could result in human extinction.