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

Mainstream projects use two heavy hydrogen isotopes called deuterium and tritium. — Aman Tripathi, Interesting Engineering, 2 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

Six tritium tube slots around the bit storage are designed to improve visibility in dark conditions. — Maryna Holovnova, New Atlas, 28 Aug. 2026

Moreover, tritium is easier to produce than plutonium, which has to be created in a costly and complex technological process that involves the irradiation of uranium in a nuclear reactor. — Tereza Pultarova, IEEE Spectrum, 10 Aug. 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