Answer:
Critical point
Step-by-step explanation: A critical point of a function y = f (x) is a point (c, f (c)) on the graph of f (x) at which either the derivative is 0 (or) the derivative is not defined. But how is a critical point related to the derivative? We know that the slope of a tangent line of y = f (x) at a point is nothing but the derivative f' (x) at that point.