Multivalued function

An example of a multifunction: the input 3 is associated with both the output b and the output c.

A multivalued function (multifunction) is a relation like a function. A multifunction associates each input with at least one output. A strict function associates each input with exactly one output. An example of a multivalued function is the square root. Every complex number (except for 0), has two square roots. Example: $\sqrt{4}$ could be 2 or -2 because $2^2=4$ and $(-2{)}^2=4$.