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

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.

Two small slots on each of those sides are there to hold available tritium vials so that the Apex V2 glows, making it (and the release buttons) easier to find in the dark. — New Atlas, 22 Oct. 2026 Unlike conventional nuclear reactors, City Labs develops microscopic power sources that generate electricity and heat through the natural decay of tritium. — Christopher McFadden, Interesting Engineering, 16 Oct. 2026 That couple could snatch either another neutron to make tritium, or another proton to make helium-3. — Cara Giovanetti, The Conversation, 25 Sep. 2026 See All Example Sentences for tritium

Word History

Etymology

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

First Known Use

1933, in the meaning defined above

Time Traveler

The first known use of tritium was in 1933

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Browse Nearby Words

tritish

tritium

trito-

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Cite this Entry

Style

“Tritium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tritium. Accessed 27 Oct. 2026.

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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

tritium

noun

Examples of tritium in a Sentence

Word History

Browse Nearby Words

Cite this Entry

Kids Definition

Medical Definition

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