Numeral system
A numeral is a way to represent a number. It may be a symbol or a word in a natural language, or a group of them. Numerals differ from numbers just as the word "rock" differs from a real rock. The symbols "11", "eleven" and "XI" are all numerals that represent the same number. Babylonian numerals, Greek numerals and Roman numerals are among the systems that were long used, before the Hindu–Arabic numeral system largely replaced them.