A Small Reminder on Roman Numerals

Earl Morse Wilbur used Roman numerals to enumerate the chapters in his book Out Unitarian Heritage.

Just in case you need a refresher, here are the basics:

• One is an uppercase i:  I
• Two is written with two uppercase i's:  II
• Three:  III
• Four:  IV
• Five:  V

Notice that a I (one) left of the V (five) means a subtraction of one.  A I (one) to the right of the V (five) means an addition of one— 5 plus 1.

• Six:  VI
• Seven:  VII
• Eight:  VIII
• Nine:  IX
• Ten:  X

A I (one) left of X (10) means subtract one from 10.

Also, the maximum number of integers you can put together is three.  So:

• 20:  XX
• 23:  XXIII
• 24:  XXIV
• 25:  XXV
• 30:  XXX
• 38:  XXXVIII
• 39:  XXXIX
• 40:  XL
• 50:  L
• 100:  C
• 500:  D
• 1000:  M

An X (10) left of L (50) means subtract 10 from 50.

But you would never say LLL for 150.  150 is written CL, as this means 100 plus 50.

So, MDCCCXXXVIII means 1,000 plus 500, plus 300, plus 30, plus 8; or, 1838.   This is perhaps the largest expression for a year you can write in the second millennium that ended in December 2000.

• 1900 is written MCM, or 1,000 plus {1,000 minus 100}.
• 1990 is written MCMXC, or 1,000 plus {1,000 minus 100: 900}, plus {100 minus 10: 90}.
• 1998 is written MCMXCVIII, 1990 plus 8.
• 1999:  MCMXCIX
• 2000:  MM.

In the new third millennium (which began in January 2001 and will end in December 3000), our years are easy to write:

• 2001:  MMI
• 2002:  MMII
• 2003:  MMIII
• 2004:  MMIV
• etc.
• 2998:  MMCMXCVIII
• 2999:  MMCMXCIX
• 3000:  MMM

But who knows if people will know anything about Roman numerals by December 3000.

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Text taken from a 1925 original copy of Earl Morse Wilbur's Our Unitarian Heritage.
Copyright released by Wilbur's grandchildren.
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