insanity

 
Pronunciation: /ɪnˈsanəti/

noun

[mass noun]
  • the state of being seriously mentally ill; madness: he suffered from bouts of insanity
  • extreme foolishness or irrationality: it might be pure insanity to take this loan [count noun]: the insanities of our time

Origin:

late 16th century: from Latin insanitas, from insanus (see insane)