illusion

American  

[ih-loo-zhuhn] / ɪˈlu ʒən /

noun

1. something that deceives by producing a false or misleading impression of reality.

   Synonyms:

   chimera, fantasy, aberration

2. the state or condition of being deceived; misapprehension.

3. an instance of being deceived.

4. Psychology. 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 very thin, delicate tulle of silk or nylon having a cobwebbed appearance, for trimmings, veilings, and the like.

6. Obsolete. the act of deceiving; deception; delusion.

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illusion British  

/ ɪˈluːʒən /

noun

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. 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. a very fine gauze or tulle used for trimmings, veils, etc

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Related Words

illusion, hallucination, delusion refer to false perceptions or ideas. An illusion is a false mental image produced by misinterpretation of things that actually exist: A mirage is an illusion produced by reflection of light against the sky. A hallucination is a perception of a thing or quality that has no physical counterpart: Under the influence of LSD, Terry had hallucinations that the living-room floor was rippling. A delusion is a persistent false belief: A paranoiac has delusions of persecution.

Other Word Forms

• illusionary
  adjective
• illusioned
  adjective

Etymology

Origin of illusion

First recorded in 1300–50; Middle English from Latin illūsiōn- (stem of illūsiō ) “irony, mocking,” equivalent to illūs(us), past participle of illūdere “to mock, ridicule” ( il- il- ¹ + lūd- play ( see ludicrous) + -tus past participle suffix) + -iōn- -ion

Explanation

An illusion is something that isn't real. It may look real, but it's actually fake — just a crafty construction or fantasy. Like the old rabbit-out-of-the-hat trick practiced by magicians around the globe. An illusion is an act of deception. Some optical illusions are pretty cool to watch, but an illusion can also point to an erroneous belief or false perception of reality, which is where you start getting into hallucination territory — seeing things that aren't there. You can give the illusion that you’re fascinated by your professor’s lecture by chewing on your pencil, furrowing your brow, and making sure to nod enthusiastically every so often.

Example Sentences

But we know that’s just an illusion, one that is dispelled by looking inside the machine.

From Slate • May 25, 2026

It is actually something of an optical illusion — for the options are not getting more expensive in terms of price as the earnings date approaches, but are remaining the same.

From MarketWatch • May 14, 2026

By presenting Satan's fall as a violent physical event instead of a purely spiritual allegory or optical illusion, Dante may have helped move Western thought toward the idea that celestial objects can directly reshape Earth.

From Science Daily • May 11, 2026

"We are under no illusion that we have a big task ahead of us," he said.

From BBC • May 8, 2026

He looks identical to the illusion except there’s a presence to him that I never felt back at Blackstone Prison.

From "Amari and the Night Brothers" by B.B. Alston

Related Words

• confusion
• deception
• delusion
• fantasy
• hallucination
• image
• misconception
• myth
• pipe dream
• semblance