Peripeteia /ˌpɛrəpɪˈteɪ.ə/ (alternative Latin form: Peripetīa, ultimately from Greek: περιπέτεια) is a reversal of circumstances, or turning point.
Aristotle, in his Poetics, defines peripeteia as "a change by which the action veers round to its opposite, subject always to our rule of probability or necessity."
This is the best way to spark and maintain attention throughout the various form and genres of drama "Tragedy imitates good actions and, thereby, measures and depicts the well-being of its protagonist.
Good uses of Peripeteia are those that especially are parts of a complex plot, so that they are defined by their changes of fortune being accompanied by reversal, recognition, or both" (Smithson).
When a character learns something he had been previously ignorant of, this is normally distinguished from peripeteia as anagnorisis or discovery, a distinction derived from Aristotle's work.
Two such plays are Oedipus Rex, where the oracle's information that Oedipus has killed his father and married his mother brings about his mother's death and his own blindness and exile, and Iphigenia in Tauris, where Iphigenia realizes that the strangers she is to sacrifice are her brother and his friend, resulting in all three of them escaping Tauris.
His parents, Laius and Jocasta, try to forestall the oracle by sending their son away to be killed, but he is actually raised by Polybus and his wife, Merope, the rulers of another kingdom.
Martin M. Winkler says that here, peripeteia and anagnorisis occur at the same time "for the greatest possible impact" because Oedipus has been "struck a blow from above, as if by fate or the gods.
After he disposes of her body, he returns home, where his son confesses that he had stolen one of the apples and that a slave, to whom he had told about his father's journey, had fled with it.