This week in math we learned the difference between a relation and function. We also learned how to tell them apart when looking at, coordinates, a mapping graph, a chart, and a cartesian graph.

A function is a special relation.  A relation is a number that has two or more Y-variables for one X-variable. A function is a number that has only one other number, so only one Y-variable is associated with an X-variable.  Another way to look at it is that the relation is a friendship and a function is a marriage.  You have many friends at a time, but only one spouse at a time.

Some examples of functions are:

Some examples of relations are:

(reasons are highlighted)

As you can see in the relation examples in every example there is at least one X-variable doubled, or they have more than one partner (y-variable). Now, these are the basics.  In some cases it gets harder and you have to pay attention to if it is opened or closed.