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

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

Examples of dementia in a Sentence

This patient suffers from dementia.

a new study on age-related dementias

Recent Examples on the Web

Regular exercise and movement amp up blood flow to the brain and slow the onset of memory loss and dementia. —Bryan Robinson, Forbes.com, 4 Apr. 2025

Unmarried older adults in the U.S. were less likely to develop dementia than those who were married, according to a new study of 24,000 Americans. —Carly Mallenbaum, Axios, 2 Apr. 2025

The family revealed months later that Willis' condition had progressed to frontotemporal dementia, or FTD. —Lauryn Overhultz, FOXNews.com, 1 Apr. 2025

Alzheimer’s disease causes irreversible nerve damage and is the leading cause of dementia. —Deborah Fuller, The Conversation, 28 Mar. 2025

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