A composite function is a function that combines two or more functions into a single function. Given two functions f(x) and g(x), the composition of functions f(x) and g(x) where g(x) is acting first is represented by f(g(x)) or (f ∘ g)(x) . In other words, the output of one function becomes the input of the other function. For example, if f(x) = 3x - 4 and g(x) = x^2, then f(g(x)) = 3(x^2) - 4.

The composition of functions is not commutative, meaning that the order in which the functions are combined matters. The domain of the composed function must be considered, and it is important to get the domain right, or we will get bad results.

Composite functions appear in one form or another in numerous programming languages. To evaluate a composite function, we can work from the "inside out" by evaluating the inner function first and then substituting that result into the outer function to find the answer.