English Reference
noun

lunacy

n.
US /ˈɫunəsi/ UK /lˈuːnəsi/ lu·na·cy UK spelling lunacies

  1. 01 C2 Proficiency Archaic

    an old-fashioned word for being mentally ill.

    an archaic term for insanity or mental derangement, historically associated with the phases of the moon.

    Simple

    In the old story, the character was locked away because of his supposed lunacy.

    In context

    The 19th-century legal documents categorized various behavioral disorders under the broad and imprecise heading of lunacy.

    Teacher's tip

    This sense is archaic and potentially offensive; modern speakers use 'mental illness' or specific clinical terms instead.


From lunatic + -cy.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level C1 · Advanced
Frequency Occasional
Updated