multivalued function

In mathematics, a multivalued function 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) ∈ Γf. If f is an ordinary function, it is a multivalued function by taking its graph They are called single-valued functions to distinguish them.