The Roman numerals for one to five are I, II, III, IV and V. The Roman numeral system assigned number values to certain letters in the Roman alphabet. By combining these letters according to their own placement rules and applying simple arithmetic, the ancient Romans were able to represent a large range of numbers.
In the Roman numeral system, I represents 1, V 5, X 10, L 50, C 100, D 500 and M 1000.
If a Roman numeral repeats, then the numeric value of that symbol is multiplied by the number of times it is indicated. Therefore, II represents 2 because I (1), is indicated twice. III represents 3 because I is indicated three times. However, no symbols except M can be used more than three times in the formation of a number. Therefore, 4 is not written as IIII.
Four, which is written as IV, illustrates another Roman counting rule. If a symbol precedes a different symbol with a larger value, then subtract the first symbol from the second symbol. Since I = 1 and V = 5, IV requires 1 to be subtracted from 5, yielding 4.
The Roman numeral system proved unwieldy for complex mathematics. Among its shortcomings is that it has no symbol for zero. In the Middle Ages, Roman numerals fell out of favor. Eventually, their widespread use was replaced by the use of Arabic numerals, which remains today. Nevertheless, vestiges of Roman numeral use remain in modern society - for instance, when Roman numerals distinguish a movie's sequel from the original, as in "The Godfather Part II."