de·​men·​tia | \ di-ˈmen(t)-shə, -shē-ə\

Definition of dementia

1 : a usually progressive condition (such as Alzheimer's disease) marked by the development of multiple cognitive deficits (such as memory impairment, aphasia, and the inability to plan and initiate complex behavior) dementia is diagnosed only when both memory and another cognitive function are each affected severely enough to interfere with a person's ability to carry out routine daily activities.The Journal of the American Medical Association
2 : madness, insanity a fanaticism bordering on dementia

Keep scrolling for more

Other Words from dementia

demential \ -​shəl \ adjective

Synonyms & Antonyms for dementia


aberration, derangement, insanity, lunacy, madness, mania, rage [archaic]


mind, saneness, sanity

Visit the Thesaurus for More 

Examples of dementia in a Sentence

This patient suffers from dementia. a new study on age-related dementias

Recent Examples on the Web

Science so far has failed to find a drug that can alter the progression of Alzheimer’s, the most common form of dementia; 146 attempts have failed over the last decade, a recent industry report found. Marilynn Marchione, The Seattle Times, "Studies in healthy older people aim to prevent Alzheimer’s," 1 Oct. 2018 However, some studies have suggested that omega-3 consumption lowers your risk of developing cognitive function issues like Alzheimer’s disease or dementia. Carolyn Todd, Allure, "Everything You Should Know Before Taking Fish Oil Supplements," 21 Aug. 2018 Other possibilities touched on are Parkinson’s disease and the devastating Lewy body dementia. Peter Keough,, "Doc Talk: A sad clown and a happy collector," 12 July 2018 For Alzheimer’s disease and other dementias, there are limited treatments and no cure. Jonel Aleccia And Melissa Bailey, USA TODAY, "Unlocked and loaded: Families confront dementia and guns," 1 July 2018 For Alzheimer’s disease and other dementias, there are limited treatments and no cure. Washington Post, "Unlocked And Loaded: Families Confront Dementia And Guns," 25 June 2018 Almost 16 million care for someone with Alzheimer’s disease or dementia. Beth Kassab,, "Loneliness comes with caregiving territory. But it doesn't have to.," 14 June 2018 Researchers recommended a new way to distinguish between Alzheimer's and other dementias. Cincinnati Enquirer,, "3 promising new developments in Alzheimer’s and dementia research," 5 June 2018 Oxidative stress is considered the main culprit in causing the diseases of aging such as cancer, heart disease and dementia. Robert Beelman, CNN, "The humble mushroom is the newest superfood," 25 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'dementia.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of dementia

1806, in the meaning defined at sense 1

History and Etymology for dementia

Latin, from dement-, demens mad, from de- + ment-, mens mind — more at mind

Keep scrolling for more

Learn More about dementia

Statistics for dementia

Last Updated

13 Jan 2019

Look-up Popularity

Time Traveler for dementia

The first known use of dementia was in 1806

See more words from the same year

Keep scrolling for more

More Definitions for dementia


de·​men·​tia | \ di-ˈmen-chə \

Medical Definition of dementia

: a usually progressive condition (as Alzheimer's disease) marked by the development of multiple cognitive deficits (as memory impairment, aphasia, and inability to plan and initiate complex behavior)

Other Words from dementia

demential \ -​chəl \ adjective

Keep scrolling for more

Comments on dementia

What made you want to look up dementia? Please tell us where you read or heard it (including the quote, if possible).


to settle judicially or to act as judge

Get Word of the Day daily email!

Test Your Vocabulary

Homophone Quiz

  • three-bears-two-of-them-look-like-theyre-whispering-to-a-third-bear-who-looks-chuffed-to-be-the-center-of-attention
  • In order to judge how people felt, the senator's office hired a firm to take a ______.
True or False

Test your knowledge - and maybe learn something along the way.

Bee Cubed

Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!