tetralogy

Tetralogy is a term used to describe a set of four related works that are intended to be experienced as a unified whole, such as a sequence of novels, plays, or films. The name comes from the Greek tetra-, four, and -logia, meaning discourse or collection. A tetralogy often centers on a single narrative arc, world, or cast of characters, with each part contributing to a cumulative plot or theme. While four-part works may be released separately, they are described as a tetralogy when the four parts are conceived as parts of one overarching project.

In classical Greek theater, a tetralogy referred to a program of four plays presented at the Dionysia: three tragedies and a satyr play. Although the four pieces formed a single program, the satyr play was distinct in tone and did not continue the tragedy narrative; the pairing is historical rather than strictly narrative.

In modern usage, tetralogies appear across literature, film, and media. Some are planned as four installments from the start, while others are grouped as tetralogies after the final part is released. The term is descriptive rather than a formal genre, and not every series of four is universally labeled a tetralogy.