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definitions

exa-

  1. a combining form used in the names of units of measure equal to one quintillion (1018) of a given base unit: exabyte.

Origin of exa-

probably ≪ Greek exō- outside, out of
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for exa-

exa-

prefix
  1. denoting 10 18exametres Symbol: E
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
exa- in Medicine

exa-

pref.
  1. One quintillion (1018):exagram.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.