What does demented mean?
"Demented" is an adjective describing a state of severe mental impairment or irrationality. In its most literal sense, it refers to someone affected by dementia — a condition marked by declining memory, judgment, and cognitive function — though modern medical usage tends to prefer person-first language such as "a person with dementia" because the adjective can carry a stigmatizing tone. More commonly in everyday speech, "demented" is used loosely and often hyperbolically to describe wild, frenzied, or seemingly insane behaviour: a demented grin, a demented scheme, a plan so reckless it defies reason. In British English particularly, it also serves as a vivid way to express exasperation, as when a persistent noise is said to be driving someone demented. Derived from the Latin de- ("away from") and mens ("mind"), the word literally means "out of one's mind." Its forcefulness makes it useful for emphasis, but its clinical association with dementia means it should be handled with care when describing real illness.
Affected by dementia or behaving as though out of one's mind; wildly irrational.
"The demented old man wandered the halls searching for a daughter who had died decades ago."
In clinical contexts, prefer person-first alternatives like "a person with dementia" to avoid stigma.
(Informal) Driven to distraction or extreme annoyance; exasperated.
"Two weeks of roadworks outside her window had left her completely demented."
Chiefly British; almost always appears in the construction "drive/driven demented."
In British English, saying something is "driving you demented" doesn't mean you're losing your mind — it's just how Brits complain about a dripping tap.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of demented
"Demented" derives from the Latin verb demens (past participle of demere-related forms), combining the prefix de- ("away from") with mens, mentis ("mind"), so its literal sense is "having lost one's mind." The word entered English via French dément in the early seventeenth century, originally meaning mad or insane. Its noun relative "dementia," from the same Latin root mens, became established as the clinical term for progressive cognitive decline, while "demented" itself drifted toward figurative and hyperbolic use. Cognates sharing the root include "mental" and "mindset," all tracing back to the Indo-European root *men-, meaning "to think."
Related word forms
How demented is actually used
When applied to people with dementia as a clinical condition, "demented" is increasingly avoided in medical and caregiving contexts in favour of person-first phrasing such as "a person with dementia," as it can sound stigmatizing. In everyday informal speech, especially in British English, it is common hyperbole for irritation ("this noise is driving me demented") or for wild, unhinged behaviour. The figurative uses are informal to colloquial.
Easily confused with demented
"Determined" means resolute and firmly decided, while "demented" means mentally deranged — the two share only a superficial sound similarity.