Appendix:Roman numerals
A Roman numerals are the numbers when it is written in the way the Romans used to write numbers.The Romans used a variety of numbers.
Overview[change]
The Roman numerals are a numerical system composed of seven English letters. They are, in this order, from lower to higher: I, V, X, L, C, D and M.
In general, the system is additive, which means that the numbers are added. As an example, 'VI' represents six, 'XIII' is thirteen.
There is a simple rule, which generally avoids that more than three of the same symbols are added. It says that the lower value symbol which is directly before the higher one, is subtracted, and not added. This rule was used in Roman times, but not at all times. It is used since about the Middle Ages. This means that rather than writing 'IIII', it is preferable to write 'IV', for the number 4 or IX, for the number 9. Also note that the subtraction rule is only valid for the symbol which comes right beforehand in the sequence. This means that 49 is written XLIX, and not IL.
When there are two letters together, each of them are worth powers of ten and the second letter is worth ten times the first, the value of this group is equal to the second letter subtracted by the first letter. Therefore, IX represents nine, XC represents ninety and CM represents nine hundred. By extension, XCIX represents ninety nine.
The numerical values of the symbols I, X, C and M are added if written up to three times together. Therefore, the number III represents three and the number MM represents two thousand.
An overline multiplies the value of a group of letters by one thousand. As an example, MV represents four thousand.
Usage notes[change]
The Arabic numerals are widely known and widely used in many languages, for example English.
Roman numerals are essentially known as upper case letters: I, V, X, L, C, D and M. However, it is possible to use lower case letters: i, v, x, l, c, d and m. Lower case Roman numerals are often seen as page numbers for materials prefatory to the beginning of the main body of a work.
List of numbers[change]
For information about number names in English, see Appendix:English numerals.