[ dih-loo-zhuhn ]
/ dɪˈlu ʒən /
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See synonyms for: delusion / delusions on Thesaurus.com

an act or instance of deluding.
the state of being deluded.
a false belief or opinion: delusions of grandeur.
Psychiatry. a fixed false belief that is resistant to reason or confrontation with actual fact: a paranoid delusion.
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Origin of delusion

First recorded in 1375–1425; late Middle English, from Latin dēlūsiōn- (stem of dēlūsiō ), equivalent to dēlūs(us) (past participle of dēlūdere; see delude) + -iōn- -ion

synonym study for delusion

1. See illusion.


de·lu·sion·al, de·lu·sion·ar·y, adjectivepre·de·lu·sion, noun


delusion , hallucination, illusion (see synonym study at illusion)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What is a delusion?

A delusion is a false belief or opinion, especially one held in resistance to strong evidence against it, as in Even after losing five straight championships, Heather still had the delusion that she was the best in the world.

In psychiatry, delusion is used to mean an unshakeable belief in something that isn’t true. They believe it because they have a mental disorder, such as schizophrenia.

More generally, delusion can be used to mean an act of deluding, as in The crowd didn’t fall for the swindler’s attempts at delusion.

Delusion can also refer to the state of being deluded, as in The emperor’s delusion was the work of the evil, scheming vizier.

Delusion is similar to the words illusion and hallucination, which also describe false beliefs or experiences. An illusion is a false image that is a result of a distortion or manipulation of actual things. For example, makeup can create the illusion that a person is younger than they actually are.

A hallucination is a false sensory experience that isn’t rooted in reality at all. On the other hand, a delusion is often somewhat based on reality but a person’s belief is inaccurate due to wrong information or their own hubris.

Example: Despite his low test scores, Gerard strongly believed the delusion that he was the smartest kid in the class.

Where does delusion come from?

The first records of the term delusion come from around 1375. It ultimately comes from the Latin dēlūdere, which means “to play false.”

When you have a delusion, you earnestly believe the false thing. If you don’t actually believe it, it’s not a delusion.

While psychiatric delusions are caused by mental disorders, general delusions are more often attributed to things like stubbornness, naiveté, or narcissism. Most of the time, we can admit we were wrong when someone shows us evidence that our belief is inaccurate. A person with delusions, however, will claim the evidence itself is wrong or fake, and it will take a tremendous amount of effort to convince them of the true reality, if they can be convinced at all.

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What are some other forms related to delusion?

  • delusional (adjective)
  • delusionary (adjective)
  • predelusion (noun)

What are some synonyms for delusion?

What are some words that share a root or word element with delusion?

What are some words that often get used in discussing delusion?

What are some words delusion may be commonly confused with?

How is delusion used in real life?

In general, the word delusion is often used to harshly criticize a person’s opinion or beliefs.

Try using delusion!

Which of the following words is NOT a synonym of delusion?

A. fantasy
B. deception
C. reality
D. misconception

How to use delusion in a sentence

British Dictionary definitions for delusion

/ (dɪˈluːʒən) /

a mistaken or misleading opinion, idea, belief, etche has delusions of grandeur
psychiatry a belief held in the face of evidence to the contrary, that is resistant to all reasonSee also illusion, hallucination
the act of deluding or state of being deluded

Derived forms of delusion

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for delusion

[ dĭ-lōōzhən ]

A false belief or perception strongly held in spite of invalidating evidence, especially as a symptom of mental illness, as in schizophrenia.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for delusion


A false belief held despite strong evidence against it; self-deception. Delusions are common in some forms of psychosis. Because of his delusions, the literary character Don Quixote attacks a windmill, thinking it is a giant.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.