Science, Tech, Math › Science Triple Point Definition and Example (Chemistry) Learn what the triple point means in chemistry Share Flipboard Email Print Triple point of water. Images Etc / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated November 18, 2019 In chemistry and physics, the triple point is the temperature and pressure at which solid, liquid, and vapor phases of a particular substance coexist in equilibrium. It is a specific case of thermodynamic phase equilibrium. The term "triple point" was coined by James Thomson in 1873. Example The triple point for water is at 0.01 degree Celsius at 4.56 mm Hg. The triple point of water is a fixed quantity, used to define other triple point values and the kelvin unit of temperature. Note the triple point may include more than one solid phase if a specific substance has polymorphs.