The 12th month of the year in the Gregorian calendar. See Table at calendar.
[Middle English decembre, from Old French, from Latin December, the tenth month of the Roman year, probably from *decemmembris, from *decem-mēnsris : decem, ten; see dek in the Appendix of Indo-European roots + mēnsis, month; see MENSES.]
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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.