These seven letters are used to make numbers. For example, the Roman numeral for 2 is written as II, just two Is are written together. The number 27 is written as XXVII, which is simply XX + V + II (20 + 5 + 2 = 27).
There is a simple rule, whenever the same symbol is written four times, it is replaced by subtracting it from the next higher number (5,50,50,500). That way, IV is written instead of IIII (4), XL instead of XXXX (40), etc. It is used since about the Middle Ages. Usually only one number is subtracted, not two. So 18 is usually XVIII instead of IIXX. Also, the subtraction rule is only valid for the symbol which comes right beforehand in the sequence. This means that 99 is written XCIX, and not IC.
|Fraction||Numeral||Name (nominative and genitive)||Meaning|
|2/12 = 1/6||·· or :||Sextans, sextantis||"Sixth"|
|3/12 = 1/4||··· or ∴||Quadrans, quadrantis||"Quarter"|
|4/12 = 1/3||···· or ∷||Triens, trientis||"Third"|
|5/12||····· or ⁙||Quincunx, quincuncis||"Five-ounce" (quinque unciae → quincunx)|
|6/12 = 1/2||S||Semis, semissis||"Half"|
|7/12||S·||Septunx, septuncis||"Seven-ounce" (septem unciae → septunx)|
|8/12 = 2/3||S·· or S:||Bes, bessis||"Twice" (as in "twice a third")|
|9/12 = 3/4||S··· or S∴||Dodrans, dodrantis
or nonuncium, nonuncii
|"Less a quarter" (de-quadrans → dodrans)|
or "ninth ounce" (nona uncia → nonuncium)
|10/12 = 5/6||S···· or S∷||Dextans, dextantis
or decunx, decuncis
|"Less a sixth" (de-sextans → dextans)|
or "ten ounces" (decem unciae → decunx)
|11/12||S····· or S⁙||Deunx, deuncis||"Less an ounce" (de-uncia → deunx)|
|12/12 = 1||I||As, assis||"Unit"|
A number of numeral systems are developed for large numbers that cannot be shown with I, V, X, L, C, D and M.
One of the systems is the apostrophus, in which D is written as IƆ (500) and M is written as CIƆ (1,000). In this system, an extra Ɔ means 500, and multiple extra Ɔs are used to mean 5,000, 50,000 etc.
Another system is the vinculum, in which V, X, L, C, D and M are multiplied by 1,000 by adding an overline.
|Wikimedia Commons has media related to Roman numerals.|
- In the Baltics and Russia, the days of the week, are often written as Roman numbers, I being Monday.
- When writing dates by hand, the month is sometimes written as a Roman numeral, especially for dates written in day-month-year sequence. For example: 26.XI.2014 or XI.26.2014 = 26 November 2014.
- When movies or books are published, the year of publication or year of copyright may be done as a Roman numeral.
- When people write about Monarchs or Popes, Patriarchs, or other leading figures, they are sometimes counted with Roman numbers, e.g. Queen Elizabeth II (of England), Pope John Paul II, Pope Benedict XVI, Patriarch Alexius II (of the Russian-Orthodox church)
- In France, the trimesters are sometimes counted with Roman numerals.
- In Poland, roman numerals are used to show the month in dates and as a short method of writing ordinals (i.e. VI to be 6th).
- Unicode has a code block called Number Forms, which also contains representations of Roman numerals, at the positions U+2160 to U+2188.
It is very easy to write a number as a Roman numeral. Simply substract the largest possible Roman numeral, as many times as possible from the number. This system will result in a valid Roman numeral, but will not take the subtraction rule into account.
|1 × 1000||+||1 × 500||+||4 × 100||+||1 × 50||+||3 × 10||+||4 × 1||=||1984|
Getting the number from the numeral is equally simple, by adding the values of the symbols.
In general, the values for 5, 50, 500,.. are not subtracted. The same number, with using the subtraction rule:
|1 × 1000||+||(−1 × 100 + 1 × 1000)||+||1 × 50||+||3 × 10||+||(−1 × 1 + 1 × 5)||=||1984|
- Gordon, Arthur E. (1982). Illustrated Introduction to Latin Epigraphy. Berkeley: University of California Press. ISBN 0-520-05079-7.
Alphabetic symbols for larger numbers, such as Q for 500,000, have also been used to various degrees of standardization.
- C. W. Jones, ed., Opera Didascalica, vol. 123C in Corpus Christianorum, Series Latina.
- "Merriam-Webster Unabridged Dictionary".
- Asimov, Isaac (1966). Asimov On Numbers (PDF). Pocket Books, a division of Simon & Schuster, Inc. p. 12.