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de·lir·i·um (dĭ-lîrē-əm)
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n. pl. de·lir·i·ums or de·lir·i·a (-ē-ə)
1. A temporary state of mental confusion and fluctuating consciousness resulting from high fever, intoxication, shock, or other causes. It is characterized by anxiety, disorientation, hallucinations, delusions, and incoherent speech.
2. A state of uncontrolled excitement or emotion: sports fans in delirium after their team's victory.

[Latin dēlīrium, from dēlīrāre, to be deranged : dē-, de- + līra, furrow; see leis-1 in the Appendix of Indo-European roots.]

de·liri·ant adj.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
 

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:

    Indo-European Roots

    Semitic Roots

    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.