mega-

1. 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

combining form

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

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] pref.

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

1. A prefix that means:
2. Large, as in megadose, a large dose.
3. One million, as in megahertz, one million hertz.
4. 220 (that is, 1,048,576), which is the power of 2 closest to a million, as in megabyte.