A ghost can be defined in several ways depending on different situations. One of the definitions refers ghost to a person's spirit or soul who has died. This definition is used commonly among all! There have been several doubts regarding the existence of the ghost and disputes too whether ghosts are just imaginations or part of objective existence. Reports say that ghosts have taken shape of vehicles, animals and humans. Parapsychologists have undertaken the task to study about ghosts.

The existence of ghost is met with the shape they exist which is usually in human shape very rarely animal ghost are encountered. It is said that it does not consists of any solid matter. Different parts of the world have different theories about the ghosts. The Western theory related to ghosts is that ghost is semi-transparent and does not interact or touch any physical objects directly. They state that paranormal ghosts are souls that could not find rest after death and they wander here and there to fulfill their goals. It is said that this is the time for them to take revenge thus killing people and making hindrances as seen in many of the movies.

There are many who do not accept the existence of ghosts. Scientific research disbelieves the fact that ghosts are disembodied souls or spirit, but then they prove that these ghosts are impressions of psychic energy left behind by a deceased person who is still living. They state that any tragedy in a person's life might cause mental energy of some kind, which would be released to the world, and this energy might be experienced by many other people who are sensitive to the presence of such energy.

Ectoplasm is referred by the parapsychologists as the substance from which spirits and ghosts are made of. Such an explanation of ghost classifies it in the same category as that of preternatural unexplained phenomena as telekinesis or poltergeists, ESP and telepathy. Such a definition always makes it difficult to explain about the ghosts that tend to answer questions and those which foretell the future etc.

An astonishing fact is that the best details about the existence of ghost can be obtained from Garuda Purana, which is script from Vedic tradition of the Hindu religion. This Purana says that people who do sins will be reborn as ghosts. Garuda Purana explains the things done by the ghosts and the food they eat. It is said that they consume vomit, waste, cough, urine and tears and prefer these to be the things that they eat and drink.

In many cases, human psychology plays a major role in ghost sightings. In chilling situations where ghosts are associated with a natural animal response may make the hair rise which could be mistaken for a chill. Illusions can be created by one by seeing an eerie figure. This occurs as a result of the disability to sharply distinguish shapes in case of peripheral vision. It is a proved fact that sound waves with frequency lower than 20 hertz called infrasound is inaudible, but now it is proved by the British scientist Richard Lord and Richard Wiseman that these infrasound would be the reason for causing humans to feel a presence in the room or even to cause unexplained feelings of dread or anxiety!