radix
The ratio, R, between the weights of adjacent digits in positional representation of numbers. The right-most digit has weight one, the digit to its left has weight R, the next R^2, R^3, etc. The radix also determines the set of digits which is zero to R-1. E.g. decimal (radix ten) uses 0-9 and each digit is worth ten times as much as you move left along the number.