Ghost was a term employed to refer to the disembodied spirits of deceased humans.
The words ghost and guest come from the German word Geist. In most early belief systems, ghosts were the spirit of ancestors, who were invited to events, ceremonies such as Samhain - or Halloween.
In Europe the head or the skull were decorated and preserved and the spirits were considered as presents. After being given an offering the spirits were consulted as oracles.
Influences from major belief systems
When Christianity came to Europe these customs were forbidden, because of the church's doctrine of the resurrection of the body insisted that a buried body should be kept as whole as possible. The hanging of the heads of executed traitors on pikes and gates represented a threat to a kind life. Even when the church had forbidden this the preserving of heads continued. Still in the days of Henry VIII of England, the daughter of Sir Thomas More retrieved the head of her father and instead of burying it, she kept it to the day she died - this is no doubt the source of many ghost stories such as "The Headless Horseman".
Other belief systems says that ghosts are the restless spirits of people, who died violently, committed suicide, were buried in unconsecrated ground or was possessed by evil spirits. There seems to be universal agreement that a ghost is a spirit of someone, or something, who has died.
- Willow: “But why is it here? Does it just want to scare people?”
- Giles: “It doesn't know exactly what it wants. That's the problem. Many times the spirit is plagued by all manner of worldly troubles. But, being dead, it has no way to make its peace. So it lashes out. Growing ever more confused, ever more angry.”
- — Willow and Giles[src]
A ghost is the spirit of a dead person, who can't find eternal peace and have to walk the earth, trying to find it. It has unresolved issues and one of the only way to get rid of a ghost is to solve the problems. One other way is Exorcism.
- Xander: “Oh, no, not cool. This was no wimpy chain-rattler. This was more like - 'I'm dead as hell and I'm not gonna take it anymore”
- Giles: “Exactly. Despite the Xander-speak, that's an accurate definition of a poltergeist.”
- Xander: “I defined something? Accurately? Check me out. Guess I'm done with the book learning!”
- — Xander and Giles[src]
A variant of the standard ghost is the poltergeist or "noisy ghost". A poltergeist is a very violent ghost, who not only can wreak havoc, but also possess individuals and force them to repeat the act, which doomed it in the first place.
Physiology and powers
A ghost can only be visible to the human eye with ectoplasm. When Spike was rendered incorporeal following the Battle at the Hellmouth, Fred's scans indicate that Spike is technically not a ghost: he lacked ectoplasm, which would make him invisible to human eyes, radiated body heat, whereas ghosts absorb heat and make the area around them a few degrees colder, and had detectable brainwaves ("Just Rewards"), so there seem to be different kinds of disembodied spirits other than ghosts.
Different cultures have adopted different "takes" on ghosts. An example is the Japanese ghosts have no feet and are drawn to water.
Though incorporeal, ghosts and other such non-corporeal beings (with the apparent exception of the First Evil) are capable of limited interaction with the physical world through intense concentration.
- In Where the Wild Things Are, the house is haunted by children.
- In Amends, Angel sees "ghosts" of people he have killed, though it is the First Evil.
- Like in Amends, the First Evil is supposed to be several "ghosts" in Conversations with Dead People.
- It is the same thing in Gingerbread with the two children, whom we first think are ghosts.