stylistic:tone, information:classification, information:filtering, linguistic:voice_change, structural:reformatting
In mathematics, a multivalued function (also known as a multiple-valued function) is a function that has two or more values in its range for at least one point in its domain. It is a set-valued function with additional properties depending on context. The terms multifunction and many-valued function are sometimes also used.

A multivalued function of sets f : X → Y is a subset

Write f(x) for the set of those y ∈ Y with (x,y) ∈ Γ. If f is an ordinary function, it is a multivalued function by taking its graph

They are called single-valued functions to distinguish them.