dementia

noun

de·​men·​tia di-ˈmen(t)-shə How to pronounce dementia (audio)
-shē-ə
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
demential adjective

Examples of dementia in a Sentence

This patient suffers from dementia. a new study on age-related dementias
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Globally, over 10 million cases of dementia are diagnosed each year, with Alzheimer’s contributing a large portion of the burden. Juergen Eckhardt, Forbes.com, 22 July 2025 The film is a part of the Mama Joe Project, which is spreading awareness on the challenges that can arise when caring for aging family members, especially when diseases like Alzheimer’s and other forms of dementia emerge. Zuri Primos july 21, Kansas City Star, 21 July 2025 There are two forms of Lewy body dementia: Dementia with Lewy bodies (DLB) and Parkinson's disease dementia. Anthony Robledo, USA Today, 12 July 2025 This adds a new dimension to long-term use of anticholinergic drugs, which have already been linked to dementia. New Atlas, 11 July 2025 See All Example Sentences for dementia

Word History

Etymology

borrowed from Latin dēmentia "derangement, insanity, folly," noun derivative of Latin dēment-, dēmens "out of one's mind, frenzied, insane," from dē- de- + -ment, -mens, adjective derivative of ment-, mens "power of reason, mental balance, mind" — more at mind entry 1

First Known Use

1806, in the meaning defined at sense 1

Time Traveler
The first known use of dementia was in 1806

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Cite this Entry

“Dementia.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/dementia. Accessed 25 Jul. 2025.

Kids Definition

dementia

noun
de·​men·​tia di-ˈmen-chə How to pronounce dementia (audio)
1
: a condition of the brain that is marked especially by a deterioration in the ability to think, reason, or remember
2
: a condition of deteriorating mental functioning

Medical Definition

dementia

noun
de·​men·​tia di-ˈmen-chə How to pronounce dementia (audio)
: 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)
demential adjective

More from Merriam-Webster on dementia

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