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

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

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

From The Wall Street Journal • Dec. 28, 2025

KATRIN's exceptionally low background means that nearly all detected electrons originate from tritium decay, allowing for a very clean measurement of the energy spectrum.

From Science Daily • Dec. 27, 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

If tritium was the sought-after product, for example, you used lithium-6; if it was plutonium, the raw material would be uranium—namely, that waste U-238.

From "Big Science" by Michael Hiltzik