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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Synonym Usage

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

Derived Forms

• illusioned
  adjective
• illusionary
  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

Appeared in the January 6, 2026, print edition as 'The ‘International Law’ Illusion'.

From The Wall Street Journal • Jan. 5, 2026

His works include 1930s classic "La Grande Illusion", following two French prisoners of war trying to escape German captivity during World War I.

From Barron's • Nov. 25, 2025

The event, which was being filmed for TV, concentrated largely on the star's latest album, Radical Optimism, with the set list including hits like Houdini, Training Season and Illusion.

From BBC • Oct. 18, 2024

Folkenflik: You know, there’s this great movie, Grand Illusion, have you ever seen that?

From Slate • Sep. 18, 2024

Illusion or not: unless Hazel could figure out how to get out of this maze, the traps would kill them.

From "The House of Hades" by Rick Riordan

Related Words

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