<Li> While in standard usage subtractive notation is limited to use of "adjacent" numerals, so that 99 (for example) is written XCIX, forms such as IC are not unknown . </Li> <Li> XIIX or IIXX are sometimes used for "18" instead of XVIII . The Latin word for "eighteen" is often rendered as the equivalent of "twenty less two", which may be the source of this usage . </Li> <Li> Sometimes V and L are not used, with instances such as IIIIII and XXXXXX rather than VI or LX . </Li> <Ul> <Li> Clock faces that use Roman numerals normally show IIII for four o'clock but IX for nine o'clock, a practice that goes back to very early clocks such as the Wells Cathedral clock of the late 14th century . However, this is far from universal: for example, the clock on the Palace of Westminster in London (aka "Big Ben") uses a "normal" IV . </Li> <Li> At the beginning of the 20th century, different representations of 900 (conventionally CM) appeared in several inscribed dates . For instance, 1910 is shown on Admiralty Arch, London, as MDCCCCX rather than MCMX, while on the north entrance to the Saint Louis Art Museum, 1903 is inscribed as MDCDIII rather than MCMIII . </Li> </Ul>

How do you write a number in numerals