A function family is a group of functions that have similar characteristics. A parent function is the most basic function in a function family. One example of a function family is the linear functions. All linear functions have a constant rate of change.

The linear parent function is $f(x)=x.$ Notice that its slope is $1$ and its $y$-intercept is $(0,1).$ Functions that belong to a family of functions are all transformations of the parent function.