Peripeteia

n. sudden change in events, sudden reversal of circumstances (especially in a literary work)

Peripeteia (Greek, ) is a reversal of circumstances, or turning point. The term is primarily used with reference to works of literature. The English form of peripeteia is Peripety. Peripety is a sudden reversal dependent on intellect and logic.Aristotle defines it as "a change by which the action veers round to its opposite, subject always to our rule of probability or necessity."Peripeteia includes changes of character, but also more external changes. A character who becomes rich and famous from poverty and obscurity has undergone peripeteia, even if his character remains the same.
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Noun
1. a sudden and unexpected change of fortune or reverse of circumstances (especially in a literary work); "a peripeteia swiftly turns a routine sequence of events into a story worth telling"
(synonym) peripetia, peripety
(hypernym) surprise