base 11 is a positional numeral system with eleven as its base. It uses 11 different digits for representing numbers. The digits for base 11 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and a.
duodecimal (base 12)
The duodecimal system (also known as base 12 or dozenal) is a positional notation numeral system using twelve as its base.