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

Deuterium–tritium fusion is the most readily attainable reaction for terrestrial fusion power, operating at lower temperatures than other leading fuel combinations. — Atharva Gosavi, Interesting Engineering, 31 Oct. 2026

The complex was built in the 1950s to produce tritium and plutonium for US nuclear weapons. — Emma Tucker, CNN Money, 29 Oct. 2026

The facility was constructed in the 1950s, when five reactors were built to produce materials used in nuclear weapons, primarily tritium and plutonium-239. — Bonny Chu , Michael Sinkewicz, FOXNews.com, 29 Oct. 2026

The Savannah River Site is a massive complex where the federal government once produced materials used in nuclear weapons, primarily tritium and plutonium-239. — ABC News, 28 Oct. 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