# critical point

### noun

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.

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## RELATED WORDS

## Nearby words

- critical density,
- critical mass,
- critical organ,
- critical path analysis,
- critical period,
- critical pressure,
- critical ratio,
- critical region,
- critical state,
- critical temperature

## Origin of critical point

First recorded in 1875–80

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

## critical point

### noun

physics

- the point on a phase diagram that represents the critical state of a substance
- another name for critical state

maths the US name for stationary point

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

## critical point

Physics The 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.

The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.