# insanity

/ˌɪnˈsænəti/ (US) · /ɪnsˈænɪti/ (UK) · CEFR B2 · Noun

Source: https://englishreference.com/word/insanity
Updated: 2026-05-02

## Definition

the state of being seriously mentally ill or acting in a very foolish way. You use this word to describe behavior that makes no sense or seems dangerous.

For teachers: a state of extreme mental illness or severe cognitive impairment; colloquially, behavior that is extremely foolish or irrational. Often used in legal contexts to describe a lack of responsibility for one's actions.

## Examples

- It would be pure insanity to drive in this storm.
- The defense lawyer argued that his client was suffering from temporary insanity at the time of the incident.
- The philosopher argued that the modern obsession with constant productivity is a form of collective insanity that ignores the fundamental human need for rest and reflection.

## Usage notes

- Uncountable in both its medical and colloquial senses; rarely takes a plural form except in highly specialized literary contexts.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.