In mathematics, the power set of a set S, written as P ( S ) {\displaystyle P(S)} or P ( S ) {\displaystyle {\mathcal {P}}(S)} , is the set of all subsets of S. In terms of cardinality, a power set is larger than the set it originates from. If S is a finite set with n elements, then P ( S ) {\displaystyle P(S)} would have 2 n {\displaystyle 2^{n}} elements.