A ghost is seen as a bodyless soul or spirit of a dead person or animal.

As unlikely as it may seem, ghosts and hauntings are a mainstream area of belief. Studies in the UK and the USA show that between 30% and 50% of the population believe in ghosts. Belief in ghosts appears to be global. Since ghosts are contrary to nature's laws as we understand them, it calls for an explanation.

• Ghosts have often been thought of as vehicles for justice. In Kenya, a murdered person may become a Ngoma - a spirit who pursues their murderer. In Russia, the rusalka is a spirit of a woman who drowned and now lures men to their death. She may be released when her death is...