 Roman numerals are essentially a decimal or "base 10" number system, with a "digit" for each power of ten – thousands, hundreds, tens and units.Each digit is represented by a fixed symbol or combination of symbols.In the absence of "place keeping" zeros, different symbols are used for each power of ten but each follows the same pattern, as summarised in this table
The numerals for 4 () and 9 () are written using "subtractive notation", where the first symbol () is "subtracted" from the larger one (, or ), thus avoiding the clumsier (, and ).