__Relations:__Sets of ordered pairs ( x , y )

__Function:__For every value of x, there is a value of y. It will need to pass the vertical line test.

__One-To-One Function:__For every one value of x, there is only one value of y, and vice versa. It will need to pass both vertical and horizontal line test.

__Vertical line Test:__A vertical line that intersects the graph of the equation only once when moves from across on the x-axis.