Who Picked the Roman Numerals?

[Jinx]

It's always bugged me that the Roman numerals didn't try to follow the alphabet. Also, what is the next denomination after "M"? - Jinx

[Johanna]

I represents the finger. The most primitive way to count, right? All God's chillun gots fingers.

V represents the hand, a shortcut way to suggest five fingers at once.

X is just two hands added together. Two V-shapes placed end to end.

L — I don't know how L came to represent 50. You got me there.

C — abbreviation for centum.

D — again, beats me.

M — abbreviation for mille.

The numbers higher than 1,000 are shown by writing a horizontal bar over the figure, which means 'multiply by 1,000'. So M with a bar over it = 1,000,000.

[FatBaldGuy]

Who Picked the Roman Numerals? The Romans

[dtilque]

D comes from an alternate way the Romans wrote numbers over 100. 1000 was represented by a symbol that was a vertical line with loops to each side, sort of like this (|) only the straight line extended past the loops. 500 was half that symbol. That is, they left off one of the loops, which resulted in something that looked like a D.

This system could go higher. 5000 was |)) and 10,000 was ((|)). I don't think it went over 100,000 though.

[Una Persson]

Note that the real Romans reputedly used their Roman Numerals differently than we do. For example, they often used "IIII" to indicate "4", and using the variant "IV" was a shorthand that developed later on (my source says Middle Ages).

[friedo]

Cecil talks about the whole IIII vs. IV mystery in this column (http://www.straightdope.com/classics/a2_153.html).

[Johanna]

I read in an encyclopedia that the Romans didn't use IV for 4 as they normally would, because that spelled the beginning of the god-name IVPITER. So as not to be blasphemous, they substituted IIII. Similarly, in Hebrew numeration the number 15 would normally be written yod-heh (yod=10 and heh=5), but because that spelled the divine name Jah it would be sacrilegious to use it profanely, so the Hebrews substituted teth-vav (teth=9 and vav=6) for 15.

[Polycarp]

L is half of C -- graphically as well as numerically. This is hard to represent with HTML-specific symbols, but look at it this way, remembering that we're talking archaic Latin alphabet, not modern Italic or Gothic letters, here:
_
|
|_ is 100; |_ is 50.

The other way to write numbers over 3,999 besides the (I) style was with macrons -- a long bar over the top of a letter.
_
V would be 5,000
_
X would be 10,000

and so on.