# Functional Relationships

<INSERT IMAGE>

Let’s look at the paths of some basketball passes more closely.

Here is the chest pass. This graph shows a *linear* relationship. A linear relationship is a *function *that models a straight line.

**Function:** A function is a rule that assigns to each input exactly one output. The graph of a function is the set of ordered pairs consisting of an input and the corresponding output.

Watch this video to see why the ball’s path is a linear relationship.