Exponentiation's a mathematical operation, written an, involving two numbers, the base a and the exponent n. When n's a positive integer, exponentiation corresponds to repeated multiplication: » a^n = underbrace, we've |2X| = 2|X|, where 2X, usually denoted by PX,'s the power set of X; each subset Y of X corresponds uniquely to a function on X taking the value 1 for x ∈ Y and 0 for x ∉ Y. In category theory In a Cartesian closed category, the exponential operation can be used to rai… (More on Exponent)