Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Deterioration of intellectual faculties, such as memory, concentration, and judgment, resulting from an organic disease or a disorder of the brain. It is sometimes accompanied by emotional disturbance and personality changes.
  • n. Madness; insanity. See Synonyms at insanity.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A progressive decline in cognitive function due to damage or disease in the brain beyond what might be expected from normal aging. Areas particularly affected include memory, attention, judgement, language and problem solving.
  • n. madness or insanity

from the GNU version of the Collaborative International Dictionary of English

  • n. Insanity; madness; esp. that form which consists in weakness or total loss of thought and reason; mental imbecility; idiocy.

from The Century Dictionary and Cyclopedia

  • n. An extremely low condition of the mental function; profound general mental incapacity.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. mental deterioration of organic or functional origin

Etymologies

Latin dēmentia, madness, from dēmēns, dēment-, senseless; see dement.
(American Heritage® Dictionary of the English Language, Fourth Edition)

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  • "If we ask Sheila then we can't ask Ron. If I have kippers now then it's quiche for tea. Four score years is about all the ifs and thens you can take. Dementia's the sane realisation you just can't be doing with all that any more". "The Last Werewolf" by Glen Duncan

    February 25, 2012

  • His father had developed dementia and began to lose memories of even his family.

    May 9, 2011