dementia

American  

[dih-men-shuh, -shee-uh] / dɪˈmɛn ʃə, -ʃi ə /

noun

• dementias
  plural

1. a condition characterized by progressive, persistent, severe impairment of intellectual capacity, including memory loss, confusion, and emotional instability, resulting from the loss of or damage to neurons in the brain.

---

dementia British  

/ -ʃɪə, dɪˈmɛnʃə /

noun

1. a state of serious emotional and mental deterioration, of organic or functional origin

---

dementia Scientific  

/ dĭ-mĕn′shə /

1. Deterioration of intellectual faculties, such as memory, concentration, and judgment, sometimes accompanied by emotional disturbance and personality changes. Dementia is caused by organic damage to the brain (as in Alzheimer's disease), head trauma, metabolic disorders, or the presence of a tumor.

---

Other Word Forms

Derived Forms

• demential
  adjective

Inflected Forms

Nouns

• dementias
  plural

Etymology

Origin of dementia

First recorded in 1800–10; from Latin dēmentia “madness,” equivalent to dēment- “out of one's mind” ( see dement) + -ia noun suffix

Compare meaning

How does dementia compare to similar and commonly confused words? Explore the most common comparisons:

• dementia vs. senility

Explanation

If your grandfather suffers from dementia, he has a brain disorder that's causing him to gradually lose his memory and become disoriented and confused. Although dementia is most common in elderly people, it's not a normal part of growing older but a syndrome caused by brain disease or injury. Dementia gets its name from the Latin words de, or "without," and mens, or "mind," which join together to mean "madness," although in English, dementia is not the same thing as madness. One example of an illness that causes dementia is Alzheimer's disease.

Example Sentences

See Examples For:

dementia dementias

Jeffries was declared "mentally incompetent" by a court last year and said to be suffering with dementia and late onset of Alzheimer's disease.

From BBC ● Aug. 21, 2026

Jeffries had claimed he was suffering from severe dementia and was unfit to proceed to trial.

From The Wall Street Journal ● Aug. 21, 2026

Even if I’m talking about getting diagnosed with depression or my mom’s dementia, I want it to feel relatable and like bringing light to harder things.

From Los Angeles Times ● Aug. 18, 2026

Lifestyle factors — such as diet, sleep, regular exercise, managing blood pressure and blood sugar, avoiding tobacco and alcohol — can reduce the risk of dementia by up to 45%, Tan said.

From MarketWatch ● Aug. 17, 2026

From some need of his own, Don Bernardo pretended his wife was just under the weather rather than suffering from dementia.

From "In the Time of the Butterflies" by Julia Alvarez

Meinor loved her job in public health, and had been developing a program for Alzheimer’s and related dementias.

From The Wall Street Journal ● Apr. 25, 2026

It could also help identify people at higher risk of developing Alzheimer's disease and related dementias, even before any symptoms appear.

From Science Daily ● Apr. 22, 2026

Or, I should say, diseases, plural — because in addition to the well-known Alzheimer’s, there are a variety of others, including frontal-lobe dementias — such as the one taking Willis — and many others.

From MarketWatch ● Feb. 11, 2026

It also interferes with how brain cells manage fats and energy and promotes inflammation, which may gradually damage neurons and increase vulnerability to Alzheimer's and related dementias.

From Science Daily ● Jan. 23, 2026

In benign stupor purely mental stimuli may change the whole clinical picture abruptly and with this produce a change in the intellectual functioning such as we never see in organic dementias or clouded states.

From Benign Stupors A Study of a New Manic-Depressive Reaction Type by John T. (John Thompson) MacCurdy

Related Words

• brain damage
• mental disorder