A fictional universe is a self-consistent fictional setting which contains its own background elements including history and geography, and possibly also fantasy or science fiction elements such as magic or a means of faster than light travel, or other derived background elements. A fictional universe may also be called a fictional realm, imaginary realm, fictional world, imaginary world or imaginary universe. Most fictional universes are based directly or indirectly on our own universe, like the familiar "with a twist" world depicted in the popular Harry Potter series.
It is difficult to determine what actually constitutes a "fictional universe", but whether the universe is contained in a single work or consists of a succession of works, such as frequently appears in fantasy or science fiction series, the universe will be self-consistent and follow an established set of rules. Its history and geography are well-defined, and even languages may be constructed as well. When subsequent works are written within the same universe, care must be taken to ensure that established rules (canon) are not violated.
