 # Roman numbers

As its name indicate, Roman numbers or numerals were developed in Europe during and after the Roman empire. Romans needed a notation system to calculate, so they chose letters to write their figures.

One curious thing you must learn, however, is that, despite the fact today Roman numerals are...

I – V – X – L – C – D – M

...they were not always like that.

## Why those letters and not others?

I found something interesting about the origin of Roman numerals. According to my reading, the symbols were chosen because...

+ I resembled a finger pointing up
+ V resembled an open hand, or five fingers
+ X our two arms crossed in front of ourselves, representing our ten fingers
+ L resembled our hand in an L position; that is, with the thumb extended and our other four fingers together; while,
+ C was a contraction of the Latin word centum, hundred.

I did not find why they chose the letter D for five hundred, but I did find they did not use the letter M for the thousand. This usage appeared somewhat later, during the first part of the Middle Ages.

How did they represent larger numbers then? They used either parenthesis or a bar on top of the number. These symbols indicated you needed to multiply the figure by 1000. For example, two thousand was represented like this: (I)(I). It is not indicated like that any more.

Besides, they represented a number four with four one symbols (IIII). The subtracted way we know today (IV) appeared later.

## Roman numbers today

Nowadays, Roman numbers are not used to carry out mathematical operations, so this shouldn't become a big deal for anybody. We write Roman numbers from the greater amount to the smaller one, and using a maximum of three equal symbols in a row. Instead of using a fourth equal symbol, we indicate numbers four or nine placing the next number and a unit of the previous kind in its left, indicating a subtraction.

Romans did not use the figure zero, so there isn't a Roman numeral for it.

Thus, we have:

+ one = I
+ two = II
+ three = III
+ four = IV (five minus one)
+ five = V
+ six = VI (five plus one)
+ seven = VII
+ eight = VIII
+ nine = IX (ten minus one)
+ ten = X

+ thirty = XXX
+ forty = XL (fifty minus ten)
+ a hundred forty-seven = CXLVII
+ a thousand nine hundred seventy-nine = MCMLXXIX

...And, for numbers over three thousand, we respect the bar Romans used in the past, indicating that the number must be multiplied by one thousand:

+ two thousand = MM
+ three thousand = MMM
+ four thousand five hundred sixty-six = IVDLXVI

Interesting, isn't it?

Continue with... Mayan numerals

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