2. Derivative means that when the independent variable X of the function y=f(x) generates an increment δ x at point x0, the limit A of the ratio of the increment δ y of the function output value to the increment δ x of the independent variable tends to 0. If it exists, a is the derivative at x0, which is denoted as f'(x0) or df/dx(x0).

3. For example, y = 2x 2-3x+4 has a second derivative with a derivative value of 4.