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Origin of demented

First recorded in 1635–45; dement + -ed2
Related formsde·ment·ed·ly, adverbde·ment·ed·ness, nounhalf-de·ment·ed, adjectivesem·i·de·ment·ed, adjective

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verb (used with object) Obsolete.
  1. to make mad or insane.

Origin of dement

1535–45; < Late Latin dēmentāre to deprive of mind, equivalent to Latin dēment- (stem of dēmēns) out of one's mind (dē- de- + ment- (stem of mēns) mind) + -āre infinitive suffix Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for demented


  1. mad; insane
Derived Formsdementedly, adverbdementedness, noun


  1. (intr) to deteriorate mentally, esp because of old age
  2. (tr) rare to drive mad; make insane

Word Origin for dement

C16: from Late Latin dēmentāre to drive mad, from Latin de- + mēns mind
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

Word Origin and History for demented

1640s, from obsolete dement "drive mad."



1540s, "to drive mad," probably from Middle French démenter, from Late Latin dementare "to drive out of one's mind," from phrase de mente (a less technical term than insanitas), from de + mente, ablative of mens mind" (see mind (n.)).

Online Etymology Dictionary, © 2010 Douglas Harper

demented in Medicine


  1. Mentally ill; insane.
  2. Suffering from dementia.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.