Fancy, fantasy, phantasy, phantasm, vision, dream, daydream, nightmare are comparable when they denote a vivid idea or image, or a series of such ideas or images, present in the mind but having no concrete or objective reality.
Fancy (see also IMAGINATION ) is applicable to anything which is conceived by the imagination, whether it recombines the elements of reality or is pure invention.
Fantasy applies to a fancy and especially to an organized series of fancies (as one presented in art) that is the product of an unrestrained imagination freed from the bonds of actuality.
Phantasy, though sometimes used in place of fantasy, both as the power of free inventive imagination and as a product of that power, may apply particularly to the image-making power of the mind, whether the image is the result of sense perception or of the imagination, or to a product of that power and then may be strongly antonymous to truth and reality.
Phantasm may be applied either to a phantasy, the mental image or to a fantasy, especially to one that is hallucinatory.
Vision often implies an imagining, but it as frequently implies a seeing or a revelation. Specifically, however, the term is applied to something which the mind perceives as clearly or concretely as if revealed to it by a supernatural or mysterious power (see REVELATION ), or as if viewed by a kind of spiritual sight or intuition, or as if seen in a dream; vision therefore often suggests a sight of something that is actually spiritual in essence or is beyond the range or power of the eyes or mind to grasp as a whole.
Dream is the general term for the ideas or images present to the mind in sleep.
In extended use dream, like daydream, suggests vague or idle, commonly happy, imaginings of future events or of nonexistent things.
Nightmare applies to a frightful and oppressive dream which occurs in sleep or, by extension, to a vision or, sometimes, an actual experience which inspires terror or which cannot easily be shaken off.