Mega-

Mega is a unit prefix in the metric system denoting a factor of one million (106 or 1 000  000). It was confirmed for use in the International System of Units (SI) in 1960. Mega comes from the Greek μέγας megas, meaning "great".

Other common examples of usage

 * megapixel - 1 million pixels in a digital camera
 * one megatonne (of TNT) (a unit often used in measuring the explosive power of nuclear weapons) is the approximate energy released on igniting one million tonnes of TNT.
 * megahertz — frequency of electromagnetic radiation for radio and television broadcasting, GSM, etc. 1 MHz = 1,000,000 Hz.

Exponentiation
When units occur in exponentiation, such as in square and cubic forms, any size prefix is considered part of the unit, and thus included in the exponentiation.
 * 1 Mm2 means one square megametre or the size of a square of 1 000  000  m by 1  000  000  m or 1012  m2, and not 1  000  000  square metres (106 m2).
 * 1 Mm3 means one cubic megametre or the size of a cube of 1 000  000  m by 1  000  000  m by 1  000  000  m or 1018 m3, and not 1  000  000  cubic metres (106 m3)

Computing
In computing, mega may sometimes denote 1,048,576 (220) of information units (example: a megabyte, a megaword), but denotes 1 000  000 (106) units of other quantities, for example, transfer rates: 1  megabit/s = 1  000  000  bit/s. The prefix mebi has been suggested as a prefix for 220 to avoid ambiguity.