A trilogy (from Greek τρι- tri-, "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, or video games. 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." Trilogies—and series in general—are common in science fiction and fantasy.