Question

What is the fundamental difference between a function and a a relation form a set A to a set B ?

Answer 1

For function every elements belonging to A must be 'n' have an image and that too unique. In a relation of particular elements belonging to A may not must have image at all in B or if it is has an image. It need not be unique i.e. It can have so many images, every mapping is a relation but every relation is not mapping.