Duodecimal

The duodecimal system (also known as base-12 or dozenal) is a positional notation numeral system using twelve as its base. In this system, the number ten may be written as "A", "T" or "X", and the number eleven as "B" or "E" (another common notation, introduced by Sir Isaac Pitman, is to use a rotated "2" for ten and a reversed "3" for eleven). The number twelve (that is, the number written as "12" in the base ten numerical system) is instead written as "10" in duodecimal (meaning "1 dozen and 0 units", instead of "1 ten and 0 units"), whereas the digit string "12" means "1 dozen and 2 units" (i.e. the same number that in decimal is written as "14"). Similarly, in duodecimal "100" means "1 gross", "1000" means "1 great gross", and "0.1" means "1 twelfth" (instead of their decimal meanings "1 hundred", "1 thousand", and "1 tenth").