inverse function

noun1

1. •
   For a given function f, another function, denoted f⁻¹, that reverses the mapping action of f; (formally) given a function f:X→Y, a function g:Y→X such that, ∀x∈X,f(x)=y⟹g(y)=x.

   • Halving is the inverse function of doubling.
   • If an inverse function exists for a given function, then it is unique.