In mathematics, a multiplicative inverse or reciprocal for a number x, denoted by or x−1, is a number which when multiplied by x yields the multiplicative identity, 1. The multiplicative inverse of a fraction is Dividing 1 by a real number yields its multiplicative inverse. For example, the reciprocal of 5 is one fifth (1/5 or 0.2), and the reciprocal of 0.25 is 1 divided by 0.25, or 4. The reciprocal function, the function f(x) that maps x to is one of the simplest examples of a function which is its own inverse (an involution).