Illusion

Illusions belong together with hallucinations to changes in perception, or perception disorders.
 * It originates from misinterpreted stimulus (which differs from hallucinations, in which new objects are perceived)
 * They tend to be presented both in psychological disorders (e.g. as a part of delirium or psychosis)and completely physiologically (typically visual illusions).

Related articles

 * Hallucination
 * Perception and its disorders