Roman Numeral X is the symbol for the number 10. It is one of the seven symbols used in the system of Roman Numerals, which was used by the ancient Romans to represent numbers. The symbol for 10 is an X, which is derived from the Latin word 'decem' meaning TEN. The other symbols used in the system are I, V, L, C, D and M. Roman Numerals are still used today in some contexts, such as clock faces and book chapters.