**
Amplitude
** -
One-half the distance between the minimum and maximum value of a
periodic
function.

**
Graph
** -
A drawing of the coordinate plane with points
plotted on it.

**
Phase Shift
** -
The constant by which functions
are horizontally shifted from one another.

**
Shift
** -
The vertical or horizontal movement of the graph of a
function without changing the
shape of the graph.

**
Stretch
** -
The vertical or horizontal changing of the graph of a
function such that its shape
changes, but its orientation does not--for a function *f*, *f* (0, 0) remains the
same.

**
Vertical Line Test
** -
A method to determine whether a given plotted line on a graph is a
function. If a vertical line can
be placed somewhere in the coordinate plane such that it intersects with the
graph twice, the graph is not a function. Two intersections with a vertical
line signify that for a given value of *x*, there are two possible values of *f* (*x*),
which by definition is impossible for a function.