And higher derivatives are also used for approximating functions using Taylor polynomials, which can be useful when a certain amount of precision is required. Because the derivative of a function y = f( x) is itself a function y′ = f′( x), you can take the derivative of f′( x), which is generally referred to as the second derivative of f(x) and written f“( x) or f 2( x). This differentiation process can be continued to find the third, fourth, and successive derivatives of f( x), which are called higher-order derivatives of f( x).