Fantasy

The Encyclopedia of Fantasy, by John Clute and John Grant, offers a definition of fantasy as stories about the impossible, that which cannot possibly exist in reality as we know it. When set in the world we know, the tales are about the impossible: beings, settings, and events that cannot be. When placed in a realm not of this earth, the settings themselves are impossible, not functioning according to our world's physical laws. Science fiction, by contrast, describes that which might be possible, though not at the present time or with known technology.