triple point

All states coexist

The triple point is the specific temperature and pressure at which a substance exists simultaneously as solid, liquid, and gas in equilibrium.

Water's triple point—0.01°C at 611.657 pascals—was long used to define the kelvin.

The term extends figuratively to any situation where three states or conditions converge: The negotiations reached a triple point where all parties' interests briefly aligned.

phases

solid

Firm matter state

liquidFree-flowing substance
gasFormless, expanding substance
coexistenceSimultaneous presence together

water · sublimation · melting · freezing · vaporization · condensation · deposition · vapor pressure · ice · steam

thermodynamics

calibration

Adjusting for measurement accuracy

temperature scaleNumbered heat-measuring system
enthalpyThermodynamic total heat quantity
entropyQuantified chaos in systems

latent heat · specific heat · isothermal · isobaric · calorimetry · thermogram · cryogenics · supercritical · invariant · degrees of freedom

measurement

standard

Level of quality accepted

referenceDirecting attention elsewhere
thermometerHeat-measuring instrument
calibrationAdjusting for measurement accuracy

SI unit · definition · precision · reproducibility · metrology · absolute zero · benchmark

Opposites

phase coexistence

triple pointsingle phase

One alternating current waveform

critical point · melting point · boiling point

phase multiplicity

triple pointsingle phase

One alternating current waveform

liquid phase · gas phase

Family

triple, pointer, triplets, triplet, tripled, point, punctuation, tripling, triply

Familiarity: Top 500,000
Profile: Used worldwide · Timeless · Rated G