# An Introduction to the Roman Numeral System in Modern Use

The Roman numeral system is commonly used to identify monarchs and popes. The Roman number behind the name will specify how many monarchs or popes have the same name. It clarifies who we are referring to. This obviously is quite useful information.

An example would be Queen Elizabeth II. This refers to the second queen with the name Elizabeth and therefore it is to be read as “Queen Elizabeth the second”.

Roman numbers may also be used to sort the different chapters of a book, state the year a building was raised, on clocks and so on.

The Roman numeral system is based on seven letters which with different combinations read as a number.

 The Seven Letters: I 1 V 5 X 10 L 50 C 100 D 500 M 1000
 Numbers 1 -10 I 1 II 2 III 3 IV 4 V 5 VI 6 VII 7 VIII 8 IX 9 X 10

A smaller number value in front of a larger number value means we need to subtract the smaller from the larger.

For example IV = 4 (5-1) – subtract the smaller from the larger when the smaller number is on the left side of the larger number.

The opposite happens if the smaller number is on the right side of the larger number; in that case you need to add the smaller number to the larger number.

Important rules:

I (1) can only be subtracted from V (5) and X (10).

X (10) can only be subtracted from L (50) and C (100)

C (100) can only be subtracted from D (500) and M (1000).

You can only subtract one number value.

The numbers V (5), L (50) and D (500) can only be added never subtracted.

The numbers V (5), L (50), and D (500) obviously are never repeated. For example the number 10 is written X, not VV.

The number value I (1) and C (100) can only appear three times in a row.

There is no zero in the Roman numeral system.

The year 2013 in Roman numerals is MMX111 (M=1000) + (M=1000) + (XIII=13).

Number 495 in Roman numbers is CDXCV (CD=400) + (XC=90) + (V=5)

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6. VinaySahu

I always wonder, is there any significance of the letters used to denote the values? Probably C means century and M means millenium.. but what about the rest?? if D means decade, should it not be used to represent 10??