<strong>Definition:</strong> Triple Point is the <a href="https://www.thoughtco.com/temperature-definition-602123" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">temperature</a> and <a href="https://www.thoughtco.com/definition-of-pressure-in-chemistry-604613" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="2">pressure</a> at which <a href="https://www.thoughtco.com/definition-of-solid-604648" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="3">solid</a>, <a href="https://www.thoughtco.com/definition-of-liquid-604558" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="4">liquid</a>, and <a href="https://www.thoughtco.com/vapor-definition-chemistry-glossary-602131" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="5">vapor</a> <a href="https://www.thoughtco.com/definition-of-phase-in-chemistry-604603" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="6">phases</a> of a particular substance coexist in equilibrium. A specific case of <a href="https://www.thoughtco.com/definition-of-phase-in-chemistry-604603" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="7">phase</a> equilibrium.<br/><br/><strong>Examples:</strong> The triple point for water is at 0.01° Celsius at 4.56 mm Hg.<p><strong><a href="https://www.thoughtco.com/a-to-z-chemistry-dictionary-4143188" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="8">Return to the Chemistry Glossary Index</a></strong></p>