A critical point refers to a specific condition in a system where a small change can lead to significant effects. In physics and thermodynamics, it often describes the temperature and pressure at which a substance's liquid and gas phases become indistinguishable. For example, at the critical point of water, it transitions from liquid to gas without a distinct boiling phase. In mathematics, a critical point is where a function's derivative is zero or undefined, indicating potential maximum or minimum values. Understanding critical points helps in analyzing the behavior of functions, such as finding the highest or lowest points on a graph, which is essential in fields like economics and engineering.