Tritium

n. isotope of hydrogen with an atomic weight of three (Chemistry)

Tritium (symbol T or ³H) is a radioactive isotope of hydrogen. The nucleus of tritium (sometimes called triton) contains one proton and two neutrons, whereas the nucleus of protium (the most abundant hydrogen isotope) contains no neutrons. Its atomic mass is 3.0160492. It is a gas (T2 or ³H2) at standard temperature and pressure. Tritium combines with oxygen to form a liquid called tritiated water T2O or partially tritiated THO.
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Noun
1. a radioactive isotope of hydrogen; atoms of tritium have three times the mass of ordinary hydrogen atoms
(hypernym) hydrogen, H, atomic number 1

n. tritium, isotope of hydrogen with an atomic weight of three (Chemistry)

n. tritium