A relation is a set of data. A function is a set of data that has one distinct output for each input. A relation is a function when an input appears only once in the data set. Here are some examples of relations:

**Collection of points**:

{(-1,2), (-2,4), (-3,6), (-1,-2)}**Table:**Look at the table,*Number of text messages sent.***Graph:**Click on**More Images**and view the graph,*Advertising Campaign Results*.

Please realize that all functions are not lines. Rolling hills, v-shaped pictures, u-shaped diagrams -these are other functions that you'll explore as an Algebra student.