Radix

In mathematical numeral systems, the radix or base is the number of unique digits, including zero, that a positional numeral system uses to represent numbers. For example, for the decimal system (the most common system in use today) the radix is ten, because it uses the ten digits from 0 through 9.

In any numeral system (except unary, where radix is 1), the base will always be written as "10". For example, "10" represents the number ten in the decimal system; "10" represents the number two in a base two system.