## Precalculus (6th Edition) Blitzer

Algebraically, a linear function is a polynomial with the highest exponent equal to $1$ or of the form $y=c$, where $c$ is a constant. A nonlinear function is all other functions. An example of a nonlinear function is $y={{x}^{2}}$. It is a nonlinear function because, although it is a polynomial, its highest exponent is $2$ and not $1$. Hence, the system is called nonlinear.