### Monotonic relationships

What is a monotonic relationship?
 A monotonic relationship between two variables is a relationship where: as one variable goes up, the other variable also goes up, or as one variable goes up, the other variable goes down Figures A and B below show examples of monotonic relationships. In both figures, as the variable $x$ increases, the variable $y$ also increases. Figure C shows an example of a non-monotonic relationship. In this figure, as the variable $x$ increases, the variable $y$ first increases but then decreases, which makes the relationship non-monotonic.