Definition
Roman numeral
A Roman numeral represents a number with the letters I, V, X, L, C, D, and M.
What it means
Each Roman letter has a value. Usually you add the values as you read. In approved smaller-before-larger pairs, such as IV or IX, subtract the smaller value instead. Roman numerals do not use ordinary base-ten place value.
Remember it
Read letter values; add usually, subtract only in approved pairs.
Example
XLIV represents 44. XL is 50 − 10 = 40, and IV is 5 − 1 = 4, so XLIV = 40 + 4 = 44.
Watch for
IL is not the standard Roman numeral for 49. Write 49 as XLIX: 40 + 9.
Common mix-up
A smaller letter before a larger one does not always make a valid subtraction pair; use the conventional forms.
Exact meaning
A Roman numeral is a numeral in the Roman system, using I, V, X, L, C, D, and M and conventional additive or subtractive combinations to represent numbers.