A set-valued function, also called a correspondence or set-valued relation, is a mathematical function that maps elements from one set, the domain of the function, to subsets of another set.[1][2] Set-valued functions are used in a variety of mathematical fields, including optimization, control theory and game theory.
Set-valued functions are also known as multivalued functions in some references,[3] but this article and the article Multivalued function follow the authors who make a distinction.