In Roman numerals, the year 2009 is expressed as MMIX. The Roman numeral system represents the number one with I, five with V, 10 with X, 50 with L, 100 with C, 500 with D and 1,000 with M.
In the notation MMIX, the two Ms indicate the year 2000. The notation IX represents the number nine. When added together, these notations result in the year 2009. The year 2010 is represented by the Roman numerals MMX, and the year 1909 is represented by the Roman numeral MCMIX. In Roman numerals, when a smaller number is written in front of a larger number, the smaller number is subtracted from the larger number.