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cir·ca·di·an

(sər-kādē-ən, -kădē-, sûr′kə-dīən, -dē-)

adj.
Biology

Relating to or exhibiting approximately 24-hour periodicity.

[Latin circā, around; see CIRCA + Latin diēs, day; see dyeu- in the Appendix of Indo-European roots.]

cir·cadi·an·ly adv.

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.

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