In digital numeral systems, the number of unique digits, including the digit zero, used to represent numbers in a positional numeral system. For example, in the decimal/denary system (the most common system in use today) the radix (base number) is ten, because it uses the ten digits from 0 through 9, and all other numbers are uniquely specified by positional combinations of these ten base digits; in the binary system that is the standard in computing, the radix is two, because it uses only two digits, 0 and 1, to uniquely specify each number.
