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a. An erroneous perception of reality: Mirrors gave the illusion of spaciousness.
b. An erroneous concept or belief: The notion that money can buy happiness is an illusion.
2. The condition of being deceived by a false perception or belief: spent months flailing about in illusion.
3. Something that is erroneously perceived or construed: The animal in the shadows turned out to be an illusion.
4. A fine transparent net fabric, used for dresses or trimmings.

[Middle English illusioun, from Old French, from Late Latin illūsiō, illūsiōn-, from Latin, a mocking, irony, from illūsus, past participle of illūdere, to mock : in-, against; see in-2 + lūdere, to play; see leid- in Indo-European roots.]

il·lu′sion·al, il·lu′sion·ar′y (-zhə-nĕr′ē) adj.
il·lu′sion·less adj.


1. a false appearance or deceptive impression of reality: the mirror gives an illusion of depth.
2. a false or misleading perception or belief; delusion: he has the illusion that he is really clever.
3. (Psychology) psychol a perception that is not true to reality, having been altered subjectively in some way in the mind of the perceiver. See also hallucination
4. (Textiles) a very fine gauze or tulle used for trimmings, veils, etc
[C14: from Latin illūsiō deceit, from illūdere; see illude]
ilˈlusionary, ilˈlusional adj
ilˈlusioned adj


(ɪˈlu ʒən)

1. something that deceives by producing a false or misleading impression of reality.
2. the state or condition of being deceived; misapprehension.
3. an instance of being deceived.
4. a perception, as of visual stimuli (optical illusion), that represents what is perceived in a way different from the way it is in reality.
5. a delicate tulle of silk or nylon having a cobwebbed appearance, for trimmings, veilings, and the like.
6. Obs. the act of deceiving.
[1300–50; Middle English < Latin illūsiō irony, mocking, derivative of illūdere to mock, ridicule =-il -il1 + lūdere to play]
il•lu′sion•al, il•lu′sion•ar`y, adj.


 of painters: group of painters, 15th century.



Barmecide feast An illusion of plenty; any illusion. In The Arabian Nights, Barmecide, a wealthy Persian noble, invited the beggar Schacabac to dine with him at a banquet table laden with dishes, all empty of food. The host feigned indulgence in the illusionary banquet, and when the beggar followed suit with gusto, Barmecide repented of his joke and served the pauper a sumptuous repast. This latter aspect of the story does not figure into the meaning of the phrase; Barmecide feast retains only that aspect of the story dealing with the nonexistent fare.

cast beyond the moon To indulge in fanciful, outlandish thoughts about the future; to imagine the impossible. One definition of cast is “to calculate or conjecture, to anticipate, to forecast” (OED). The moon was considered a mysterious force of inexplicable power. Beyond the moon reinforces the idea of a realm where nothing is impossible. The phrase appeared as early as the mid-16th century.

But oh, I talk of things impossible, and cast beyond the moon. (Thomas Hey wood, A Woman Killed with Kindness, 1607)

castles in Spain Fanciful notion; pipe dream—the opposite of all that is practical, reasonable, and grounded in common sense. The phrase appeared in English in The Romance of the Rose (approx. 1400).

Thou shalt make castles then in Spain,
And dream of joy, all but in vain.

Château en Espagne, the French equivalent, dates from the 13th century. The OED attributes the reference to Spain to the fact that it represents a “foreign country where one had no standing-ground.” Spain was superseded by the now current air or sky.

castles in the air Visionary projects; daydreams or fantasies; impractical, romantic, or whimsical schemes; half-baked ideas without solid foundation. This phrase, common since 1575, is equivalent to castles in the sky.

Things are thought, which never yet were wrought,

And castles built above in lofty skies.

(George Gascoigne, The Steele Glas, 1575)

Fata Morgana See ENTICEMENT.

fool’s paradise A self-deceptive state of contentment or bliss; a mental condition in which one’s happiness is generated by delusions and false hopes. The expression is derived from the Latin limbus fatuorum, a quasi-limbo where the mentally feeble went after death. The phrase has evolved to mean the fantasy world inhabited by certain daft individuals.

You have been revelling in a fool’s paradise of leisure. (James Beres-ford, The Miseries of Human Life, 1807)

pie in the sky An illusion of future benefits and blessings which will never be realized; an unattainable state of happiness or utopia. This expression, probably alluding to the concept of pie as something sweet and desirable, and sky as in the air, beyond one’s reach, was popularized in a World War I song often attributed to Joe Hill (1927):

You will eat, bye and bye,
In the glorious land above the sky!
Work and pray,
Live on hay,
You’ll get pie in the sky when you die!

pipe dream An unrealistic and often fantastic plan, goal, or idea. One source suggests that this expression alludes to the dreams and schemes which may inspire an opium addict after he has smoked a pipeful of the drug.

tilt at windmills To combat imaginary evils, to fight opponents or injustices that are merely the figments of an over-active imagination. The allusion is to Cervantes’ Don Quixote de la Mancha, in which the hero Don Quixote imagines the windmills he has come upon to be giants and proceeds to do battle, with the result that both the knight and his horse are injured and his lance destroyed. At this Quixote’s squire Sancho Panza says that anyone who mistakes windmills for giants must have windmills in his head, i.e., suffer delusions, be crazy. The equivalent French phrase is se battre contre les moulins à vent. A variant of the expression appeared in Frederic W. Farrar’s book on Christ:

Dr. Edersheim is again—so far as I am concerned—fighting a windmill.



You can use either of these words to say that someone has a wrong belief.

They have the illusion that every contingency can be worked out in advance.
One patient had the delusion that he was Trotsky.

You say that someone is under an illusion or delusion.

Finally, I think he wanted me because he was under the illusion that I was loaded with money.
I still laboured under the nice middle-class delusion that everyone was a good guy at heart.

You can also say that someone suffers from an illusion or delusion.

A man who has had a leg amputated often suffers from the delusion that the leg is still there.

If you have an illusion of something, you believe that it exists when in fact it does not.

We have an illusion of freedom.
In return they are allowed the illusion of a guiltless life.
1. another meaning of 'illusion'

An illusion is also something that looks or sounds like one thing, but is either something else or is not there at all.

It might be an optical illusion but he actually seems to lift some horses in races when they are tired.
I fancy I can hear her voice, but that must be an illusion.

You do not use delusion with this meaning.

ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.illusion - an erroneous mental representationillusion - an erroneous mental representation  
fantasm, phantasm, phantasma, phantom, shadow, apparition - something existing in perception only; "a ghostly apparition at midnight"
appearance - a mental representation; "I tried to describe his appearance to the police"
irradiation - the apparent enlargement of a bright object when viewed against a dark background
phantom limb - the illusion that a limb still exists after it has been amputated
2.illusion - something many people believe that is falseillusion - something many people believe that is false; "they have the illusion that I am very wealthy"
misconception - an incorrect conception
bubble - an impracticable and illusory idea; "he didn't want to burst the newcomer's bubble"
ignis fatuus, will-o'-the-wisp - an illusion that misleads
wishful thinking - the illusion that what you wish for is actually true
3.illusion - the act of deluding; deception by creating illusory ideas
dissimulation, deception, dissembling, deceit - the act of deceiving
4.illusion - an illusory featillusion - an illusory feat; considered magical by naive observers
performance - the act of presenting a play or a piece of music or other entertainment; "we congratulated him on his performance at the rehearsal"; "an inspired performance of Mozart's C minor concerto"
card trick - a trick performed with playing cards
prestidigitation, sleight of hand - manual dexterity in the execution of tricks


1. delusion, misconception, misapprehension, fancy, deception, fallacy, self-deception, false impression, false belief, misbelief No one really has any illusions about winning the war.
2. false impression, feeling, appearance, impression, fancy, deception, imitation, sham, pretence, semblance, fallacy Floor-to-ceiling windows give the illusion of extra space.
false impression fact, truth, reality, actuality
3. fantasy, vision, hallucination, trick, spectre, mirage, semblance, daydream, apparition, chimera, figment of the imagination, phantasm, ignis fatuus, will-o'-the-wisp It creates the illusion of moving around in the computer's graphic environment.


1. An erroneous perception of reality:
2. An illusory mental image:
3. A fantastic, impracticable plan or desire:
وَهْمٌوَهْم، صورة خادِعَه
tálmynd, tálsÿn
göz aldanmasıhayalî görüntüyanılsama
ảo tưởng


[ɪˈluːʒən] N
1. (= deceptive appearance) → ilusión f
optical illusionilusión f óptica
it gives an illusion of spacecrea una ilusión or impresión de espacio
2. (= misapprehension) → ilusión f
to be under an illusionhacerse falsas ilusiones, estar en un error
I am under no illusions on that scoresobre ese punto no me hago (falsas) ilusiones
to be under the illusion thatcreerse que ...
he was under the illusion that he would winse creía que iba a ganar
he cherishes the illusion thatabriga la esperanza de que ... + subjun


[ɪˈluːʒən] nillusion f
to be under the illusion that ... → nourrir l'illusion que ...
to have no illusions about sth → ne se faire aucune illusion sur qch
Nobody has any illusions about winning the war → Personne ne se fait aucune illusion sur l'issue favorable de la guerre.
to give the illusion of sth (= impression) → donner l'illusion de qch


nIllusion f; (= hope also)trügerische Hoffnung; (= misperception)Täuschung f; to be under an illusioneiner Täuschung (dat)unterliegen, sich (dat)Illusionen machen; to be under the illusion that …sich (dat)einbilden, dass …; to be under or have no illusionssich (dat)keine Illusionen machen, sich (dat)nichts vormachen (→ about über +acc); no one has any illusions about winning the warniemand macht sich Illusionen, dass der Krieg gewonnen werden kann; it gives the illusion of spacees vermittelt die Illusion von räumlicher Weite; a tan can give the illusion of being slimmerwenn man braun ist, kann das den Eindruck erwecken, dass man schlanker ist ? optical illusion


[ɪˈluːʒn] nillusione f
to be under an illusion → illudersi
to be under the illusion that → illudersi che
to have no illusions → non farsi illusioni


(iˈluːʒən) noun
(something that produces) a false impression, idea or belief. an optical illusion.
ilˈlusionist noun
a conjuror.


وَهْمٌ iluze illusion Illusion παραίσθηση ilusión illuusio illusion iluzija illusione 錯覚 환각 illusie illusjon iluzja ilusão иллюзия illusion ภาพลวงตา yanılsama ảo tưởng 幻想


n. ilusión, interpretación imaginaria de impresiones sensoriales.


n ilusión f
References in classic literature ?
I do want him to think I look well, and tell them so at home," said Amy to herself, as she put on Flo's old white silk ball dress, and covered it with a cloud of fresh illusion, out of which her white shoulders and golden head emerged with a most artistic effect.
When he could not shake off the illusion his mind gave it a profes- sional twist.
Perhaps the rapidity of the changes from one of these paces to the other created an optical illusion, which might thus magnify the powers of the beast; for it is certain that Heyward, who possessed a true eye for the merits of a horse, was unable, with his utmost ingenuity, to decide by what sort of movement his pursuer worked his sinuous way on his footsteps with such persevering hardihood.
There was no attempt to conceal the point of junction between Kearney's cabin and the newly-transported saloon from the flat--no architectural illusion of the palpable collusion of the two buildings, which seemed to be telescoped into each other.
He was seeking to make himself more fully sensible of the scene around him; or, perhaps, dreading it to be a dream, or a play of imagination, was vexing the fair moment with a struggle for some added brilliancy and more durable illusion.
Many a time afterwards had Hester been tortured, though less vividly, by the same illusion.
Clare had first returned from the north, impressed with the system and order of his uncle's kitchen arrangements, he had largely provided his own with an array of cupboards, drawers, and various apparatus, to induce systematic regulation, under the sanguine illusion that it would be of any possible assistance to Dinah in her arrangements.
On the whole tour, particularly at the Descent, we undergo an optical illusion which often seems to be incredible.
Her mother, sisters, Fanny, all had been conscious of his regard for her at Norland; it was not an illusion of her own vanity.
Day and night he was watching, and patiently enduring all the annoyances that irritable nerves and a shaken reason could inflict; and, though Kenneth remarked that what he saved from the grave would only recompense his care by forming the source of constant future anxiety - in fact, that his health and strength were being sacrificed to preserve a mere ruin of humanity - he knew no limits in gratitude and joy when Catherine's life was declared out of danger; and hour after hour he would sit beside her, tracing the gradual return to bodily health, and flattering his too sanguine hopes with the illusion that her mind would settle back to its right balance also, and she would soon be entirely her former self.
Never had the impenetrable atmosphere of illusion through which women behold the man of their choice -- the atmosphere which had blinded her to all that was weak, selfish, and mean in Frank's nature -- surrounded him with a brighter halo than now, when she was pleading with the father for the possession of the son.
Then, that glorious vision of doing good, which is so often the sanguine mirage of so many good minds, arose before him, and he even saw himself in the illusion with some influence to guide this raging Revolution that was running so fearfully wild.