a. The act or process of deluding.
b. The state of being deluded.
a. A false belief or opinion: labored under the delusion that success was at hand.
b. Psychiatry A false belief or perception that is a manifestation of a mental illness: delusions of persecution.
[Middle English delusioun, from Latin dēlūsiō, dēlūsiōn-, from dēlūsus, past participle of dēlūdere, to delude; see DELUDE.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.