In folklore, a ghost (sometimes known as an apparition, haunt, phantom, poltergeist, shade, specter or spectre, spirit, spook, and wraith) is the soul or spirit of a dead person or animal that can appear to the living. In ghostlore, descriptions of ghosts vary widely from an invisible presence to translucent or barely visible wispy shapes, to realistic, lifelike visions. The deliberate attempt to contact the spirit of a deceased person is known as necromancy, or in spiritism as a séance.

The belief in the existence of an afterlife, as well as manifestations of the spirits of the dead, is widespread, dating back to animism or ancestor worship in pre-literate cultures. Certain religious practice --funeral rites, exorcisms, and some practices of spiritualism and ritual magic-- are specifically designed to rest the spirits of the dead. Ghosts are generally described as solitary, human-like essences, though stories of ghostly armies and the ghosts of animals rather than humans have also been recounted. They are believed to haunt particular locations, objects, or people they were associated with in life.

The overwhelming consensus of science is that ghosts do not exist. Their existence is impossible to falsify, and ghost hunting has been classified as pseudoscience. Despite centuries of investigation, there is no scientific evidence that any location is inhabited by spirits of the dead.

While deceased ancestors are universally regarded as venerable, and often believed to have a continued presence in some form of afterlife, the spirit of a deceased person that persists in the material world (a ghost) is regarded as an unnatural or undesirable state of affairs and the idea of ghosts or revenants is associated with a reaction of fear. This is universally the case in pre-modern folk cultures, but fear of ghosts also remains an integral aspect of the modern ghost story, Gothic horror, and other horror fiction dealing with the supernatural.

Common attributes

Another widespread belief concerning ghosts is that they are composed of a misty, airy, or subtle material. Anthropologists link this idea to early beliefs that ghosts were the person within the person (the person's spirit), most noticeable in ancient cultures as a person's breath, which upon exhaling in colder climates appears visibly as a white mist. This belief may have also fostered the metaphorical meaning of "breath" in certain languages, such as the Latin spiritus and the Greek pneuma, which by analogy became extended to mean the soul. In the Bible, God is depicted as synthesising Adam, as a living soul, from the dust of the Earth and the breath of God.

In many traditional accounts, ghosts were often thought to be deceased people looking for vengeance (vengeful ghosts), or imprisoned on earth for bad things they did during life. The appearance of a ghost has often been regarded as an omen or portent of death. Seeing one's own ghostly double or "fetch" is a related omen of death.
Union Cemetery in Easton, Connecticut is home to the legend of the White Lady.

White ladies were reported to appear in many rural areas, and supposed to have died tragically or suffered trauma in life. White Lady legends are found around the world. Common to many of them is the theme of losing a child or husband and a sense of purity, as opposed to the Lady in Red ghost that is mostly attributed to a jilted lover or prostitute. The White Lady ghost is often associated with an individual family line or regarded as a harbinger of death similar to a banshee.

Legends of ghost ships have existed since the 18th century; most notable of these is the Flying Dutchman. This theme has been used in literature in The Rime of the Ancient Mariner by Coleridge.

They are often depicted as being covered in a shroud and/or dragging chains.