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  1. a combining form meaning “early,” “primeval,” used in the formation of compound words: Eocene; eohippus.

Origin of eo-

< Greek, combining form of ēṓs (Attic héōs) dawn; akin to east, Aurora


  1. ex officio.

eo ipso

[ey-oh ip-soh; English ee-oh ip-soh]
adverb Latin.
  1. by that very fact.

eo nomine

[ey-oh noh-mi-ne; English ee-oh nom-i-nee]
adverb Latin.
  1. by that name.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for eo

dawn, eos

Examples from the Web for eo

Historical Examples of eo

British Dictionary definitions for eo


combining form
  1. early or primevalEocene; eohippus

Word Origin for eo-

from Greek, from ēōs dawn


abbreviation for
  1. ex officio
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

Word Origin and History for eo


word-forming element used from mid-19c. (first in Eocene) in compound words formed by earth-scientists and meaning "characterized by the earliest appearance of," from Greek eos "dawn," from PIE *aus-, cognate with Modern English east (q.v.). Piltdown Man, before exposed as a fraud, was known as Eoanthropus.

Online Etymology Dictionary, © 2010 Douglas Harper