1. a combining form used in the names of units of measure equal to one trillion of a given base unit: terahertz.
  2. Computers. a combining form of like function with the value 240 (=1,099,511,627,766). Abbreviation: T

Origin of tera-

< Greek téras monster. See terato-
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British Dictionary definitions for tera-


  1. denoting 10 12terameter
  2. Also: tebi- denoting 2 40terabyte
Symbol: T

Word Origin for tera-

from Greek teras monster
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 tera-

prefix used in forming large units of measure (e.g. terabyte), 1947, from Greek teras (genitive teratos) "marvel, monster."

Online Etymology Dictionary, © 2010 Douglas Harper

tera- in Medicine


  1. One trillion (1012):terahertz.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

tera- in Science


  1. A prefix that means:
  2. One trillion (1012), as in terahertz, one trillion hertz.
  3. 240 (that is, 1,099,511,627,776), which is the power of two closest to a trillion, as in terabyte.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.