pl.n. (used with a sing. or pl. verb)
The 15th day of March, May, July, or October or the 13th day of the other months in the ancient Roman calendar.
[Middle English, from Old French, from Latin Īdūs, probably of Etruscan origin.]
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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.