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

Earlier, in another development related to fusion energy, IE had reported that researchers in the US are developing a method to recycle nuclear waste to make tritium – a rare version of hydrogen which serves as one of the main fuels in nuclear fusion. —Aman Tripathi, Interesting Engineering, 5 Nov. 2025

There are direct tritium beta decay experiments (like KATRIN) that are ongoing, seeking to measure the individual neutrino mass eigenstates (ν1, ν2, and ν3) directly. —Big Think, 28 Oct. 2025

Scientists have figured out how to collect helium-3 produced by the decay of tritium in nuclear weapons and power plants, but that yields less than 20 kg a year. —Jeremy Bogaisky, Forbes.com, 2 Sep. 2025

These neutrons interact with the lithium to eventually produce tritium. —New Atlas, 2 Sep. 2025

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