base 9 is a positional numeral system with nine as its base. It uses 9 different digits for representing numbers. The digits for base 9 could be 0, 1, 2, 3, 4, 5, 6, 7, and 8.
base 2
base 2 is a positional numeral system with two as its base. It uses 2 different digits for representing numbers. The digits for base 2 could be 0, and 1.