Duology

A trilogy (from Greek τρι- , "three" and -λογία -logia, "discourse") is a set of three works of art that are connected, and that can be seen either as a single work or as three individual works. They are commonly found in literature, film, and video games, and are less common in other art forms. Three-part works that are considered components of a larger work also exist, such as the triptych or the three-movement sonata, but they are not commonly referred to with the term "trilogy".

Most trilogies are works of fiction involving the same characters or setting, such as The Deptford Trilogy of novels by Robertson Davies and The Apu Trilogy of films by Satyajit Ray. 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). Trilogies can also be connected in less obvious ways, such as The Nova Trilogy of novels by William S. Burroughs, each written using cut-up technique.

The term is less often applied to music, such as the Berlin Trilogy of David Bowie, linked together by musical sound and lyrical themes, and being recorded at least partly in Berlin, Germany. The singer Adele has been quoted as saying that she "believes in trilogies", and considers her first three albums, 19, 21, and 25 to be a trilogy.

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