An origin myth is a myth that purports to describe the origin of some feature of the natural or social world. One type of origin myth is the cosmogonic myth, which describes the creation of the world. However, many cultures have stories set after the cosmogonic myth, which describe the origin of natural phenomena and human institutions within a preexisting universe. In Western classical scholarship, the terms etiological myth and aition (from the Ancient Greek αἴτιον, "cause") are sometimes used for a myth that explains an origin, particularly how an object or custom came into existence.