What is the Roman numeral for 4?

The Roman numeral for the number four is IV. The Roman numeral system uses combinations of letters to form numerals. The basic letters in the system are I for one, V for five, X for 10, L for 50, C for 100, D for 500 and M for 1,000.

No more than three of the same letters can be used consecutively in a Roman numeral. Although the number three is expressed as III, the number four has to be expressed as IV. Putting the letter of lesser value to the left of a letter with greater value indicates subtraction, while putting letters of equal or lesser value to the right of a letter indicates addition.