Relation Let A and B be two sets.
It is sufficient if some associations between elements of A and B are defined. A and B be two sets. A function f from A to B is a relation between A and B such that for each a A there is one and only one associated b B . The set A is called the domain of the function, B is called its range . Image and Preimage Let A and B be two sets and f a function from A to B .