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: [math]\displaystyle{ \sqrt{4} }[/math] could be 2 or -2 because [math]\displaystyle{ 2^2 = 4 }[/math] and [math]\displaystyle{ (-2)^2 = 4 }[/math].