mega-

variant of megalo- (megalith); also the initial element in units of measure that are equal to one million of the units denoted by the base word (megahertz). Symbol: M

Also especially before a vowel, meg-.

Origin of mega-

combining form representing Greek mégas large, great

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for mega-

mega-

combining form

denoting 10 6megawatt Symbol: M
(in computer technology) denoting 2 20 (1 048 576)megabyte
large or greatmegalith
informal great in importance or amountmegastar

Word Origin for mega-

from Greek megas huge, powerful

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 mega-

before vowels meg-, word-forming element often meaning "large, great," but in precise scientific language "one million" (megaton, megawatt, etc.), from Greek megas "great, large, vast, big, high, tall; mighty, important" (fem. megale), from PIE *meg- "great" (cf. Latin magnus, Old English micel; see mickle). Mega began to be used alone as an adjective by 1982.

High-speed computer stores 2.5 megabits [headline in "Electronics" magazine, Oct. 1, 1957]

mega- in Medicine

mega-

pref.

Large:megacephaly.
One million (106):megahertz.

mega- in Science

mega-

A prefix that means:
Large, as in megadose, a large dose.
One million, as in megahertz, one million hertz.
220 (that is, 1,048,576), which is the power of 2 closest to a million, as in megabyte.