A number's a mathematical object used in counting and measuring. A notational symbol which represents a number's called a numeral, but in common usage the word number's used for both the abstract object and the symbol, as well as for the word for the number. In addition to their use in counting and measuring, numerals are often used for labels (telephone numbers), for ordering (serial numbers), and for codes (ISBNs). In mathematics, the definition of number has been extended over the years to in… (More on Numerical)