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

This wastewater can contain small amounts of radioactive tritium, and the current ALARA objective is to keep the radiation exposure from this wastewater to 3 mrem per year or less. — Stephanie Pappas, Scientific American, 10 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

Because the isotope occurs only in tiny amounts naturally, future reactors are expected to generate their own tritium using materials such as FLiBe inside a surrounding molten salt blanket. — Neetika Walter, Interesting Engineering, 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