noun

insanity

in-SAN-uh-tee/ɪnˈsænəti/

A severe disturbance of rational mental functioning.

The lawyer raises insanity as a defense during the trial.

A respectful symbolic depiction of a distressed white adult overwhelmed by disordered swirling thoughts while a supportive clinician listens, no violent or stereotyped imagery.

Etymology

inLatinnot

+sanLatinhealthy, sound

+ityLatinstate or quality

These pieces express a state of not being sound or healthy. English used the noun for seriously impaired mental functioning, then extended it to extreme folly or irrationality.

In context

Ralph W. Campbell53:20

that there was disaster ahead and they were having to prepare for some awful eventualities and Shackleton realized this would have produced mental strain which probably would have led to insanity

Shackleton Documentary Shackleton Story Shackleton's Voyage of Endurance english subtitles

More examples

The old hospital records describe her condition as insanity.
The novel traces his gradual descent into insanity.
He is found not guilty by reason of insanity.

Forms

insane adjective — Severely impaired in rational mental functioning.

Similar words

madness: Often sounds literary or emotional rather than formal or legal.
psychosis: Specifically describes impaired contact with reality, not legal responsibility.