In fiction, canon is the material accepted as "official" in a fictional universe. It is often contrasted with, or used as the basis for, works of fan fiction. The term "canon" can be used either as a noun, referring to "the original work from which the fan fiction author borrows," or as an adjective to describe whether or not certain elements are accepted as authoritative parts of the fictional universe. Fan-fiction would be described as "non-canon," while an event from the official source material would be "canon." The alternative term mythology is often used, especially to refer to a richly detailed fictional canon requiring a large degree of suspension of disbelief (e.g. an entire imaginary world and history).