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

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

From MarketWatch • Jun. 19, 2026

The just-quirky-girls-at-a-country-club mood does eventually turn darker, but the musical, like some other works of art about mental illness, often falls into the trap of romanticizing it.

From The Wall Street Journal • Jun. 5, 2026

Maybe Pratt can actually deliver on his promise of a “treatment-led recovery model that addresses mental illness and addiction as the primary drivers of chronic homelessness.”

From Los Angeles Times • Jun. 4, 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

Some people think mental illness is a matter of mood, a matter of personality.

From "Every Day" by David Levithan

Related Words

• insanity
• mental disorder