tritium

American  

[trit-ee-uhm, trish-, trish-uhm] / ˈtrɪt i əm, ˈtrɪʃ-, ˈtrɪʃ əm /

noun

Chemistry.

1. an isotope of hydrogen having an atomic weight of three. 3 H, T

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tritium British  

/ ˈtrɪtɪəm /

noun

1. a radioactive isotope of hydrogen, occurring in trace amounts in natural hydrogen and produced in a nuclear reactor. Tritiated compounds are used as tracers. Symbol: T or ³H; half-life: 12.5 years

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tritium Scientific  

/ trĭt′ē-əm,trĭsh′ē-əm /

1. A radioactive isotope of hydrogen whose nucleus has one proton and two neutrons with atomic mass of about 3 and a half life of 12.5 years. Tritium is rare in nature but can be made artificially in nuclear reactions. It is used in thermonuclear weapons and luminescent paints, and sometimes as a tracer.

2. See more at hydrogen

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Etymology

Origin of tritium

1930–35; < New Latin < Greek trít ( os ) third ( tri- tri- + -tos adj. suffix) + New Latin -ium -ium

Example Sentences

First-generation reactors will almost certainly be fueled by the hydrogen isotopes deuterium and tritium.

From The Wall Street Journal • Dec. 28, 2025

Deuterium is abundant, but tritium is scarce because it is radioactive, with a half-life of only 12.3 years.

From The Wall Street Journal • Dec. 28, 2025

The state of Illinois sued Exelon after finding tritium in the water near one of its nuclear reactors.

From Barron's • Oct. 17, 2025

The files said one incident, in August 2019, resulted in the release of "unnecessary radioactive waste" in the form of low levels of tritium, which is used in nuclear warheads.

From BBC • Aug. 9, 2025

Teller believed a promising option to fuel a Super bomb would be to use tritium, a superheavy isotope of hydrogen.

From "Big Science" by Michael Hiltzik