What characterizes a non-linear function?

A non-linear function is characterized by its graph being a curve rather than a straight line. This means that as you plot values of the function, the relationship between the input (x-values) and output (y-values) does not change at a constant rate. In other words, the rate of change of the output with respect to the input varies. Non-linear functions can include quadratic functions, exponential functions, and trigonometric functions, among others, and their graphs can exhibit various shapes, including parabolas, circles, and waves.

In contrast, a linear function is defined by a constant rate of change, resulting in a straight-line graph. Therefore, the other options do not describe the characteristic of a non-linear function adequately.