The Story Behind Ghosts According to Wikipedia

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.