Roman Numerals

We explain what Roman numerals are, their history and what their symbols and rules are. Also, how they are used today.

What are Roman numerals?

Roman numerals or Roman numerals are the set of written symbols developed in Ancient Rome to represent quantities . These symbols were part of a numbering system used throughout the Roman Empire, which borrowed some letters from the alphabet itself, that is, it did not use specific symbols for numbers, as occurred in the systems of other cultures.

The symbols of the Roman system consisted of capital letters with a fixed numerical value which when appearing in the figure were added or subtracted, depending on their position, to create higher figures. This means that they were part of an additive and subtractive number system instead of a positional one (as is the case in the decimal system).

History of Roman numerals

Roman numerals were born as an update of the Etruscan numeral system in turn taken from the system of the ancient Greeks. The ancient Romans took the letters from their alphabet that most closely resembled the Etruscan symbols and created their own pattern. These letters are capital letters because initially the Latin alphabet did not contain lowercase letters of any kind.

The Roman system was, in its beginnings, only additive, like the Etruscan, so that the symbols were piled up to create the chosen figure (4, for example, corresponded to four units: IIII), until reaching a figure sufficiently raised to change sign (5 units: IIIIII, becomes V). But around the 3rd century BC. C. the system was perfected to also allow subtraction which gave rise to a more synthetic and pragmatic model (in which 4 is represented as IV, that is, five units minus one).

Roman numerals survived the fall of the empire and the transformation of European culture, and continued to be used for centuries, until eventually being displaced by Arabic numerals due to the influence of the Arab empires during the Middle Ages. Currently they are reserved for very specific uses, such as the titling of chapters and the numbering of some clocks, among others.

Roman numeral symbols

The Roman numeral symbols are limited, seven only, and each with a fixed value set, as shown below:

Rules of the Roman numbering system

The Roman numbering system consists, in the first instance, of the accumulation of symbols with a fixed value, arranged from highest to lowest in a linear direction from left to right . In other words, the figures must always start with the highest signs.

The figures, therefore, are composed by adding the signs that appear to the right. So, for example, if we see two or more unit signs, we must add them: I + I = II (1 + 1 = 2), and the number, therefore, grows to the right as it increases: III is I + I + I.

However, once we reach a certain amount, we must turn to signs of greater value (such as V) to which we can, however, continue adding units, as long as they appear on the right side of the figure: V + I = VI (5 + 1 = 6), for example. The same rule applies to adding higher signs: X + V = XV (10 + 5 = 15).

Thus, any figure in Roman numerals is the product of the sum of the signs that represent it. 1382, for example, is represented as follows: MCCCLXXXII, equivalent to 1000 + (100 + 100 + 100) + (50 + 10 + 10 + 10) + 1 + 1, that is, 1000 + 300 + 80 + 2 However, in no case can the same number be repeated more than three times in a row, that is, you cannot write IIII (for 4) or XXXX (for 40); In these cases, subtraction must be resorted to.

When we find a number of greater value than another, but located to the right of it, we must subtract the small number to the largest: IV = V – I (4 = 5 – 1), for example, since V is greater than I. This applies to any number: IX = X – I (9 = 10 – 1), XL = L – X (40 = 50 – 10), CD = D – C (400 = 500 – 100). This is the way to compose Roman numerals for which the same sign would need to be repeated more than three times.

Current uses of Roman numerals

Today, Roman numerals have a very limited and specific use. They are often used to number the book chapters to mark the hours of some watches and in written language to indicate the numbering of the centuries (11th century, 20th century), the numbering of the kings and nobles (Juan Carlos I, Enrique VII).

They are also used in the numbering of military divisions (IV Army Platoon, II Lancer Battalion) and the editions of certain events important (II Mariano Picón Salas Biennial of Literature, III European Congress of Astrophysics, 20th anniversary of the return of democracy).

It is also common to find them in documents from ancient times and as part of national symbols monuments and other solemn objects and places, such as the naves of a Christian church, or the stages of the Stations of the Cross of Jesus of Nazareth.

Roman numerals table

The following is a table with the Roman numerals from 1 to 1000:

References

• “Roman numerals” at https://es.wikipedia.org/
• “Etruscan numbering” at https://es.wikipedia.org/
• “Roman numerals” at the University of Murcia (Spain). https://www.um.es/
• “Spelling of Roman numerals” in the Orthography of the Language of the Royal Spanish Academy. http://aplica.rae.es/
• “Roman Numeral System” (video) on Don't Memorise. https://www.youtube.com/
• “Roman numeral (mathematics)” at https://www.britannica.com/