Of, relating to, or being the epoch of geologic time from about 56 to 34 million years ago, the second epoch of the Tertiary Period. It is characterized by warm climates, the rise of most modern mammalian families, and the formation of the Himalayas. See Table at geologic time.
The Eocene Epoch.
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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.