In literature, an epigraph is a quotation that is placed at the start of a work or section that expresses in some succinct way an aspect or theme of what is to follow.
The epigraph may serve as a banner, to link the work to a wider literary canon, either to invite comparison or to enlist a conventional context. The long quotation from Dante's Inferno that prefaces T. S. Eliot's 'The Love Song of J. Alfred Prufrock' is part of a speech by one of the damned souls in Dante's Hell. Linking it to the monologue which forms Eliot's poem adds a comment and a dimension to Prufrock's confession. The epigraph to Eliot's "Gerontion" is a quotation from Shakespeare's Measure for Measure.
The epigraphs to the preamble of Georges Perec's Life: A User's Manual (La Vie mode d'emploi) and to the book as a whole warn the reader that tricks are going to be played and that all will not be what it seems.
Some authors use fictional quotations that purport to be related to the fiction of the work itself. For example, Stephen King's Misery has epigraphs taken from the fictitious novels written by the protagonist; Jasper Fforde's The Eyre Affair has quotations from supposedly future works about the action of the story. Some science fiction authors (Isaac Asimov's Foundation Trilogy is an example) are fond of using quotations from an imagined future history of the period of their story. This can be seen as a way of claiming authenticity for a work of the imagination.
In mathematics, the epigraph of a proper convex function is the set of points lying on or above its graph:
