different between eschatology vs premillennialism

English

From Ancient Greek ??????? (éskhaton) (neuter of ??????? (éskhatos, “last”)) +? -logy.

eschatology (countable and uncountable, plural eschatologies)

(countable) System of doctrines concerning final matters, such as death.
(uncountable) The study of the end times — the end of the world, notably in Christian and Islamic theology, the second coming of Christ, the Apocalypse or the Last Judgment.

From premillennial +? -ism.

premillennialism (uncountable)

A concept in Christian eschatology that the second coming will happen before the millennium.
- 2009, Diarmaid MacCulloch, A History of Christianity, Penguin 2010, p. 912:
  Premillennialism stressed division and separation within society, to gather in the elect, and its frostiness to Enlightenment projects of social reform contributed to that peculiar process by which ‘liberal’ has become a word of abuse in the United States, in sharp contrast to its esteem in European society.

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