tritium

noun

tri·​ti·​um ˈtri-tē-əm  ˈtri-shē- 

: a radioactive isotope of hydrogen that has one proton and two neutrons in its nucleus and that has three times the mass of ordinary hydrogen

—symbol T

Examples of tritium in a Sentence

Recent Examples on the Web

On terra firma, most of the available supply of helium-3 comes as a by-product of nuclear weaponry via the radioactive decay of tritium, a rare isotope of hydrogen that boosts the power of thermonuclear bombs. — Robin George Andrews, Scientific American, 14 May 2026

Managing scarcity through digital modeling While deuterium is highly abundant and easily extracted from standard seawater, tritium is exceedingly scarce in nature. — Aman Tripathi, Interesting Engineering, 5 July 2026

Lofted atop a SpaceX Falcon 9 rocket, the Betavoltaic Orbital High-Reliability (BOHR) CubeSat is designed to demonstrate using tritium as an energy source. — David Szondy july 07, New Atlas, 8 July 2026

Word History

Etymology

New Latin, from Greek tritos third — more at third entry 1

First Known Use

1933, in the meaning defined above

Kids Definition

tritium

noun

tri·​ti·​um ˈtrit-ē-əm  ˈtrish-ē- 

: a rare radioactive form of hydrogen having atoms with three times the mass of ordinary light hydrogen atoms

Medical Definition

tritium

noun

tri·​ti·​um ˈtrit-ē-əm  ˈtrish-ē- 

: a radioactive isotope of hydrogen that has three times the mass of ordinary hydrogen

—symbol T