mental illness

American  

noun

mental illnesses plural

1. any of the various forms of psychosis or severe neurosis.

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mental illness British  

noun

1. any of various disorders in which a person's thoughts, emotions, or behaviour are so abnormal as to cause suffering to himself, herself, or other people

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mental illness Scientific  

/ mĕn′tl /

1. Any of various psychiatric disorders or diseases, usually characterized by impairment of thought, mood, or behavior.

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Other Word Forms

Noun Inflected Forms

• mental illnesses
  plural

Etymology

Origin of mental illness

First recorded in 1960–65

Example Sentences

See Examples For:

mental illness

Financial independence isn’t always possible for everyone, especially when faced with challenges including physical and mental illness.

From MarketWatch ● Jun. 19, 2026

Homelessness can cause mental illness, and mental illness can cause addiction, and vice versa.

From Los Angeles Times ● Jun. 6, 2026

Likewise, at a time when homosexuality was charged as a crime and classified as a mental illness, plenty of men who loved men married women, and plenty of women who loved women married men.

From Salon ● Jun. 3, 2026

Court psychiatrist Peter Hoffmann said Beran A showed no signs of mental illness, adding that there was "no psychiatric explanation" for his radicalisation.

From BBC ● May 28, 2026

Some of them like him and—he thinks—know of mental illness firsthand and so understand him.

From "Vincent and Theo: The Van Gogh Brothers" by Deborah Heiligman

Related Words

• insanity
• mental disorder