An exponential function is a function that has a constant growth factor. This means that it grows by equal factors over equal intervals.

For example, \(f(x)=2 \boldcdot 3^x\) defines an exponential function. Any time \(x\) increases by 1, \(f(x)\) increases by a factor of 3. 

In an exponential function, the output is multiplied by the same factor every time the input increases by 1. This multiplier is called the growth factor.