# Roman numerals

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**Roman numerals** are a numeral system that was used by ancient Rome. Numbers in this system uses letters from the Latin alphabet. Currently, it uses seven symbols:^{[1]}

The Europeans still used Roman numerals even after the fall of the Roman Empire. From the 14th century, the Europeans replaced Roman numerals with Arabic numerals. However, people still uses the Roman numerals to this day.

One place they are sometimes seen is on clock faces. For example, on the clock of Big Ben, the hours from 1 to 12 are written as:

**I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII**

The IV and IX can be read as "one less than 5" (4) and "one less than 10" (9). On most Roman numeral clock faces, however, 4 is written as IIII.^{[2]}

## Subtraction rule[change | change source]

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**.

## Special values[change | change source]

### Zero[change | change source]

The number zero does not have its own Roman numeral. About 725, Bede or one of his colleagues used the letter **N**, the abbreviation (short form) of *nihil* (the Latin word for "nothing").^{[3]}

### Fractions[change | change source]

The Romans also used fractions. The most common base for fractions was 1/12, which in Latin is called *uncia* (ounce).

Fraction | Numeral | Name (nominative and genitive) | Meaning |
---|---|---|---|

1/12 | · | Uncia, unciae | "Ounce" |

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, dodrantisor nonuncium, nonuncii | "Less a quarter" (de-quadrans → dodrans)or "ninth ounce" (nona uncia → nonuncium) |

10/12 = 5/6 | S···· or S∷ | Dextans, dextantisor 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" |

### Large numbers[change | change source]

A number of numeral systems are developed for large numbers that cannot be shown with I, V, X, L, C, D and M.

#### Apostrophus[change | change source]

One of the systems is the *apostrophus*,^{[4]} in which **D** is written as **IƆ** (500) and **M** is written as **CIƆ** (1,000).^{[5]} In this system, an extra **Ɔ** means 500, and multiple extra **Ɔ**s are used to mean 5,000, 50,000 etc.

Numeral | IƆ | CIƆ | CIƆƆ | IƆƆ | CCIƆƆ | CCIƆƆƆ | CCIƆƆƆƆ | IƆƆƆ | CCCIƆƆƆ | CCCIƆƆƆƆ | CCCIƆƆƆƆƆ | CCCIƆƆƆƆƆƆ |
---|---|---|---|---|---|---|---|---|---|---|---|---|

Value | 500 | 1,000 | 1,500 | 5,000 | 10,000 | 10,500 | 15,000 | 50,000 | 100,000 | 100,500 | 105,000 | 150,000 |

#### Vinculum[change | change source]

Another system is the *vinculum*, in which **V**, **X**, **L**, **C**, **D** and **M** are multiplied by 1,000 by adding an overline.

Numeral | V | X | L | C | D | M |
---|---|---|---|---|---|---|

Value | 5,000 | 10,000 | 50,000 | 100,000 | 500,000 | 1,000,000 |

## Usage[change | change source]

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.

### Write years[change | change source]

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 |

M | + | D | + | CCCC | + | L | + | XXX | + | IIII | = | MDCCCCLXXXIIII |

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 |

M | + | CM | + | L | + | XXX | + | IV | = | MCMLXXXIV |

## Related pages[change | change source]

## References[change | change source]

- ↑ 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.

- ↑ "The Mathematical Tourist : IIII versus IV on Clocks". Ivars Peterson. Retrieved 31 May 2019.
Expressed as Roman numerals, the first twelve numbers are usually given as I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII. However, on many clock faces, when the numbers on the dial are in Roman numerals, IIII replaces IV.

- ↑ 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.