Nouns

(n)molarity, molar concentration, Mconcentration measured by the number of moles of solute per liter of solution
(n)thousand, one thousand, 1000, M, K, chiliad, G, grand, thou, yardthe cardinal number that is the product of 10 and 100
(n)megabyte, M, MBa unit of information equal to 1000 kilobytes or 10^6 (1,000,000) bytes
(n)megabyte, mebibyte, M, MB, MiBa unit of information equal to 1024 kibibytes or 2^20 (1,048,576) bytes
(n)M, mthe 13th letter of the Roman alphabet