Trilogy

A trilogy is a set of three works of art, usually literature, film, or video games, that are connected and can be seen either as a single work or three individual works. Most trilogies are works of fiction involving the same characters or setting, such as The Deptford Trilogy of novel by Robertson Davies or The Godfather films of Francis Ford Coppola. Others are connected only by theme: for example, each film of Krzysztof Kieślowski's Three Colors trilogy explores one of the political ideals of the French Republic (liberty, equality, fraternity) and each novel in Paul Auster's The New York Trilogy uses formats from detective fiction to explore existential questions. Trilogies can also be connected in less obvious ways, such as "The Nova Trilogy" of novels by William S. Burroughs, each written using Brion Gysin’s cut-up technique. Trilogies and series in general are common in science fiction and fantasy because of the artistic importance of complex ideas and the commercial importance... full article at wikipedia