A ghost story may be any piece of fiction, or drama, that includes a ghost, or simply takes as a premise the possibility of ghosts or characters' belief in them. The "ghost" may appear of its own accord or be summoned by magic. Linked to the ghost is the idea of "hauntings", where a supernatural entity is tied to a place, object or person. Ghost stories are commonly examples of ghostlore. Colloquially, the term "ghost story" can refer to any kind of scary story. In a narrower sense, the ghost story has been developed as a short story format, within genre fiction. It is a form of supernatural fiction and specifically of weird fiction, and is often a horror story. While ghost stories are often explicitly meant to be scary, they have been written to serve all sorts of purposes, from comedy to morality tales. Ghosts often appear in the narrative as sentinels or prophets of things to come. Belief in ghosts is found in all cultures around the world, and thus ghost stories may be passed down orally or in written form.