\(
\begin{array}{|l|l|}
\hline \text { Linear Functions } & \text { Nonlinear Functions } \\
\hline \begin{array}{l}
\text { A linear function is a function } \\
\text { whose graph is a straight line. }
\end{array} & \begin{array}{l}
\text { A nonlinear function is a function } \\
\text { whose graph is not a straight line. }
\end{array} \\
\hline \begin{array}{l}
\text { Its equation is of the form } f(x)= \\
a x+b .
\end{array} & \begin{array}{l}
\text { Its equation can be in any form } \\
\text { except of the form } f(x)=a x+b .
\end{array} \\
\hline \begin{array}{l}
\text { Its slope is constant for any two } \\
\text { points on the curve. }
\end{array} & \begin{array}{l}
\text { The slope of every two points on } \\
\text { the graph is not the same. }
\end{array} \\
\hline \begin{array}{l}
\text { In the table of a linear function, } \\
\text { the ratio of difference of } y \text { and } \\
\text { difference of } x \text { is a constant. }
\end{array} & \begin{array}{l}
\text { In the table of a nonlinear } \\
\text { function, the ratio of difference of } \\
y \text { and difference of } x \text { is not a } \\
\text { constant. }
\end{array} \\
\hline
\end{array}
\)