Etymologically
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delusional

This is the current revision of this entry, as edited by bogdan on 31 October 2026 at 15:30. This address is a permanent link to this version.
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Pronunciation

  • /dɪˈluːʒənəl/[1]

Etymology

It is formed from English delusion + -al.[2][3] Delusion is from Latin dēlūsiō (“a deceiving”), from dēlūdō (“to delude”), the source of delude.[3][4]

Earliest recorded meaning

Of the nature of delusion, or affected by delusions: 1858 according to Etymonline,[2] 1871, in J. R. Reynolds's System of Medicine, in the OED.[3]

Semantic evolution

The OED's first record is from a medical work, and the adjective draws on the sense of delusion as a fixed false belief, a form of mental disorder, which Etymonline dates to the 1550s.[3][2] It is now used both of a belief and of a person who holds such beliefs.[5][6]

Timeline

  • 1858 – pertaining to delusion; affected by delusions (Etymonline).[2]
  • 1871 – of the nature of delusion (the OED's first record).[3]

Meanings

Adjective

  1. Having delusions; holding false beliefs that resist evidence: He was delusional about his chances of winning.[5][6][2]
  2. Based on or of the nature of a delusion: a delusional fear of being watched.[5][3][6]

References

  1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  3. ^ a b c d e f Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  4. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
  5. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  6. ^ a b c Random House Webster's Unabridged Dictionary (1999), 2nd ed., New York: Random House