Roman numerals

Roman numerals on stern of the ship Cutty Sark showing draught in feet. The numbers range from 13 to 22, from bottom to top.

Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Like many other ancient numeral systems, Roman numerals are based on the additive principle: a number is written by concatenating individual symbols, each representing a fixed value, and the value of the resulting numeral phrase is the sum of the individual values of each letter. The modern style of Roman numerals uses only seven letters from the Latin alphabet as symbols: I meaning 1, V meaning 5, X meaning 10, L meaning 50, C meaning 100, D meaning 500, and M meaning 1000. For example, the Roman numeral XXVII represents the number 10 + 10 + 5 + 1 + 1 = 27. When a smaller numeral symbol precedes a larger one, subtraction is implied; for example, the notation IV represents 5 − 1 = 4 and IX represents 10 − 1 = 9.