dementia

noun

de·​men·​tia di-ˈmen(t)-shə 

-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

di-ˈmen(t)-shəl 

-shē-əl

adjective

Synonyms of dementia

• schizophrenia
• insanity
• hysteria
• madness
• instability

Examples of dementia in a Sentence

This patient suffers from dementia.

a new study on age-related dementias

Recent Examples on the Web

None of the participants had dementia at the start. —Tom Gavin, EverydayHealth.com, 23 Mar. 2026

Stroke, Parkinson’s disease, dementia and other neurological conditions can affect the muscles and nerves that control swallowing. —Sundeep Venkatesan, The Conversation, 23 Mar. 2026

The suburban father, who had been living a double-life as a cold-blooded hitman for years, is beginning to question his life and actions as his past catches up with him and his memory fails to serve him due to the early onset of dementia. —Saman Shafiq, USA Today, 22 Mar. 2026

Shari Bailey said she was brought to tears this week when a lawmaker texted her with the news that the House had passed a bill, inspired by her daughter, that aims to improve outcomes for people with autism or dementia who wander off. —Danielle J. Brown, Baltimore Sun, 22 Mar. 2026

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

Phrases Containing dementia

• dementia praecox
• dementia pugilistica
• senile dementia

Rhymes for dementia

• sententiae

Kids Definition

dementia

noun

de·​men·​tia di-ˈmen-chə 

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 

: 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 

adjective