Stephen P. Morse, San Francisco

I = 1There are very specific rules for how the letters are selected. Specifically:

V = 5

X = 10

L = 50

C = 100

D = 500

M = 1000

1. Starting with the highest valued letter (M), keep repeating that letter as long as the sum of all the letters does not exceed the numeric value desired.

2.Repeat step 1 for each lower-valued letter in turn.

3. Four repetitions of the same letter are not allowed. So make the following replacements (these are referred to as subtractive notation)Examples:

IIII not preceded by V => IV4. Exception: The number 4 on clocks is sometimes written as IIII instead of IV.

VIIII => IX

XXXX not preceded by L => XL

LXXXX => XC

CCCC not preceded by D => CD

DCCCC => CM

MMMM is not permitted (the highest possible number is 3999)

III = 3Large Numbers:

IV = 4

IX = 9

XXV = 25

XCIX = 99

MCMLXXXIV = 1984

1. Large numbers are sometimes written with a bar over them (Vinculum notation).

For example, V̅=5000, X̅=10000, D̅=50000, C̅=100000, etc.

2. Large numbers are sometimes written with archaic symbols.

For example, ↁ=5000, ↂ=10000, ↇ=50000, ↈ=100000, etc.

3. A modern version of the archaic symbols is the Apostrophus notation.

500 1,000 5,000 10,000 50,000 100,000 500,000 1,000,000 Vinculum D M V̅ X̅ L̅ C̅ D̅ M̅ Archaic D ↀ ↁ ↂ ↇ ↈ Apostrophus |Ↄ C|Ↄ |ↃↃ CC|ↃↃ |ↃↃↃ CCC|ↃↃↃ |ↃↃↃↃ CCCC|ↃↃↃↃ

© Stephen P. Morse, 2018