Physics. the point at which a substance in one phase, as the liquid, has the same density, pressure, and temperature as in another phase, as the gaseous.

Mathematics.

(of a function of a single variable) a point at which the derivative of the function is zero.

(of a function of several variables) a point at which all partial derivatives of the function are zero.

PhysicsThe temperature and pressure at which the liquid and gaseous phases of a pure substance become unstable and fluctuate locally within the substance. The critical point of water is at a temperature of 374°C (705.2°F) and a pressure of 218 atmospheres, at which point it becomes opaque. Compare triple point.

Mathematics

A maximum, minimum, or point of inflection of a curve.

A point at which the derivative of a function is zero, infinite, or undefined.