A ghost is said to be the apparition of a deceased person, frequently similar in appearance to that person, and usually encountered in places she or he frequented, the place of his or her death, or in association with the person's former belongings. The word "ghost" may also refer to the spirit or soul of a deceased person, or to any spirit or demon. A place in which ghosts are supposed to appear is described as haunted. A related phenomenon is the poltergeist, literally a 'noisy spirit' that manifests itself by moving and influencing objects, though a widespread view today is that these occurences are either fraudulent or manifestations of the psychic energy of, particularly, adolescent girls. Phantom armies, animals, trains and ships have also been reported.The reality of ghosts is a vexed subject which divides believers and skeptics.The study of ghosts is both the subject of folklore and also, since the nineteenth century, of the investigations of parapsychologists, who have attempted to refine the vocabulary used in describing ghostly phenomena. Summoning or exorcising the shades of the departed is an item of belief and religious practice for spiritualists and practitioners of ritual magic. Though some claims of ghostly phenomena are proven frauds others remain unexplained or are subject to conflicting explanations. So far no one explanation has gained universal acceptance.