Nonlinear Function

A nonlinear function, as its name suggests, is a function that is not linear. In other words, the graph of a nonlinear function is not a straight line. i.e., its graph can be anything other than a straight line. Nonlinear functions will always form a curved graph. The curve of the graph will depend upon the degree of the function. The higher the degree, the higher the curvature.

An example of a nonlinear equation is
\(
a x^2+b x=c .
\)
As you can see, the degree of the equation is 2, so it is a quadratic equation. If we increase the degree to 3, it will be a cubic equation.

Some more examples are 

Examples of nonlinear functions
\(
\begin{aligned}
& 2 x^2+3 x=4 \\
& 3 x^2-4 x+10=0 \\
& 3 x^3+6 x^2+3 x=4
\end{aligned}
\)