# delusion

/dɪˈɫuʒən/ (US) · /dɪlˈuːʒən/ (UK)

Source: https://englishreference.com/word/delusion
Updated: 2026-08-08

## Senses

### 1. false belief

noun · CEFR C1 · Formal

a belief in something that is not true, which you keep even when people show you proof that you are wrong.

For teachers: a firm, fixed belief in something false, maintained despite incontrovertible evidence to the contrary.

- He was under the delusion that he could win the race without any training.
- The patient suffered from the persistent delusion that he was being monitored by a foreign intelligence agency despite all evidence to the contrary.

Usage: Often used with the preposition 'under' as in 'under the delusion that'.

### 2. the act of misleading

noun · CEFR C2 · Formal · Literary

the act of tricking someone or the state of being tricked into believing something false.

For teachers: the process of deluding or the state of being deluded; the act of deceiving oneself or others.

- The company's success was a total delusion created by dishonest accounting.
- The political campaign was built on a foundation of public delusion, masking the true economic consequences of the proposed policies.

## Examples

- He is under the delusion that he can win without practicing.
- The patient suffered from the delusion that he was being followed by secret agents despite having no evidence.
- The company's leadership operated under the collective delusion that their market share was untouchable, ignoring the rapid technological shifts that eventually led to their bankruptcy.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.