A fantasy is a situation imagined by an individual or group, which does not correspond with reality but expresses certain desires or aims of its creator. Fantasies typically involve situations which are impossible (such as the existence of magic powers) or highly unlikely. Fantasies can also be sexual in nature.
When used in psychoanalytic writings in the English language, "phantasy" with the "ph" spelling, generally refers to the unconscious psychic content of the drives. Fantasy with an 'f' spelling is used to refer to more conscious psychic content such as day dreaming and productions of the imagination. See Object relations theory for further discussion.
An adult who constantly seems to be living in a fantasy world may be considered a Walter Mitty character.