a combining form meaning “early,” “primeval,” used in the formation of compound words: Eocene; eohippus.
English Affixes From A To Z: A One-Stop List Of Suffixes, Prefixes, and Combining FormsIn English, we love to make new words by adding all sorts of bits to the front and back of existing terms. These are called affixes, and they are added to the base or stem of a word. When attached to the end of word, the affix is called a suffix. And to the beginning? A prefix.
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British Dictionary definitions for eo-
early or primevalEocene; eohippus
Word Origin for eo-
from Greek, from ēōs dawn
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012