one of the numerals in the ancient Roman system of notation, still used for certain limited purposes, as in some pagination, dates on buildings, etc. The common basic symbols are I (=1), V (=5), X (=10), L (=50), C (=100), D (=500), and M (=1000). The Roman numerals for one to nine are: I, II, III, IV, V, VI, VII, VIII, IX. A bar over a letter multiplies it by 1000; thus, X̅ equals 10,000. Integers are written according to these two rules: If a letter is immediately followed by one of equal or lesser value, the two values are added; thus, XX equals 20, XV equals 15, VI equals 6. If a letter is immediately followed by one of greater value, the first is subtracted from the second; thus, IV equals 4, XL equals 40, CM equals 900. Examples: XLVII(=47), CXVI(=116), MCXX(=1120), MCMXIV(=1914). Roman numerals may be written in lowercase letters, though they appear more commonly in capitals.

the letters used by the Romans for the representation of cardinal numbers, still used occasionally today. The integers are represented by the following letters: I (= 1), V (= 5), X (= 10), L (= 50), C (= 100), D (= 500), and M (= 1000). If a numeral is followed by another numeral of lower denomination, the two are added together; if it is preceded by one of lower denomination, the smaller numeral is subtracted from the greater. Thus VI = 6 (V + I), but IV = 4 (V – I). Other examples are XC (= 90), CL (= 150), XXV (= 25), XLIV (= 44). Multiples of a thousand are indicated by a superior bar: thus, ̅V = 5000, ̅X = 10 000, ̅X̅D = 490 000, etc

Letters of the alphabet used in ancient Rome to represent numbers: I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000. The numbers one through ten are written I, II, III, IV, V, VI, VII, VIII, IX, and X. Roman numerals are often used to signify divisions of a long work, or of a work with many parts. They are also used to lend significance to something, as in Super Bowl VII. Formal designation of years may also be in Roman numerals: a.d. MCMLXXXIX = a.d. 1989.