Look up mega- in Wiktionary, the free dictionary. Mega is a unit prefix in metric systems of units denoting a factor of one million (10 6 or 1 000 000 ). It has the unit symbol M. It was confirmed for use in the International System of Units (SI) in 1960. Mega comes from Ancient Greek: μέγας, romanized : mégas, lit. ‘great’.
https://en.wikipedia.org/wiki/Mega-

