A composite function is when one function is substituted into another. For the composite function       f (g(x)), or "f of g of x", the output of the function g(x), is the input for the function f (x). This is equivalent to  which can be expressed as "f composed with g at x."  

Khan Academy Practice:

• Find Composite Functions 

• Evaluating Composite Functions

We can write a function as a composition of two simpler functions.