dementia

noun

de·​men·​tia di-ˈmen(t)-shə How to pronounce dementia (audio)
-shē-ə
Synonyms of dementianext
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
di-ˈmen(t)-shəl How to pronounce dementia (audio)
-shē-əl
adjective

Synonyms of dementia

Relevance
See All Synonyms & Antonyms in Thesaurus

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.
Researchers conducted the study by tracking health data from 132,585 patients in Denmark who were diagnosed with type 2 diabetes between 2006 and 2019 and had no prior history of statin use or dementia. — Khloe Quill, FOXNews.com, 4 Sep. 2026 This may be particularly important for women, who have a higher life expectancy and therefore a higher lifetime risk of cognitive decline and dementia. — Mira Miller, Verywell Health, 3 Sep. 2026 Several studies have also found that vaccination is associated with a lower risk of dementia and may even slow the onset of cognitive impairment. — Editorial Board, Washington Post, 3 Sep. 2026 Why the process fails in some cases is an open question, one that future investigations could now explore to open new avenues in dementia prediction and treatment. — Mike McRae 03, New Atlas, 3 Sep. 2026 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

Phrases Containing dementia

Rhymes for dementia

See All Rhymes for dementia

Browse Nearby Words

démenti
dementia
demential
See all Nearby Words

Cite this Entry

“Dementia.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/dementia. Accessed 6 Sep. 2026.

Copy Citation

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
-chəl How to pronounce dementia (audio)
adjective

More from Merriam-Webster on dementia

Britannica.com: Encyclopedia article about dementia

Last Updated: - Updated example sentences
Love words? Need even more definitions?

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

Popular in Grammar & Usage

See More

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

A List of Most Commonly Confused Words

Why do we use apostrophes to show possession?

Is it 'nerve-racking' or 'nerve-wracking'?

What's the difference between 'fascism' and 'socialism'?
See More

Popular in Wordplay

See More

The Longest Long Words List

Stay Woke

Ye Olde Nincompoop: Old-Fashioned Words for 'Stupid'

14 Phobias You Probably Haven't Heard Of

The Words of the Week - Sept. 4
See More

Popular

See More

A Who’s Who Regarding ‘Who’s’ and ‘Whose’

The Longest Long Words List

Stay Woke
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
anagrams on a chalk board
Word Builder Quiz Vol. 2 Pick the letter that when added to a word will ma...
See All