# Function Or Not?

- Author:
- Tim Brzezinski

- Topic:
- Functions, Function Graph

Recall the following definitions:

**A relation is a correspondence between 2 sets. Algebraically, you can think of a relation as a set of ordered pairs (x,y).****Once special type of relation is called a FUNCTION.****Every function is a relation,****but not every relation is a function.****A function is a relation for which each and every input gets mapped to ONE and ONLY ONE output.**The following applets help further illustrate this concept for functions represented graphically.