1. A person who is affected by lunacy; a mentally deranged person.
2. A very foolish person.
1. Affected by lunacy; mentally deranged.
2. Of or for people who are mentally deranged.
3. Wildly or giddily foolish: a lunatic decision.
[Middle English lunatik, from Old French lunatique, from Latin lūnāticus, from lūna, moon (from the belief that madness was influenced by the phases of the moon); see leuk- in the Appendix of Indo-European roots.]
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Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.