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[trit-ee-uh m, trish-, trish-uh m] /ˈtrɪt i əm, ˈtrɪʃ-, ˈtrɪʃ əm/
noun, Chemistry
an isotope of hydrogen having an atomic weight of three.
Origin of tritium
1930-35; < New Latin < Greek trít(os) third (tri- tri- + -tos adj. suffix) + New Latin -ium -ium Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for tritium
  • When a warhead detonates, it squeezes the deuterium and tritium until they fuse together.
  • As for the amount of tritium leaked you are so utterly drastically wrong it isn't even funny.
  • Since tritium is highly radioactive, that makes containment a big problem as structures weaken and need to be replaced.
  • Thus, whatever materials are used in a deuterium-tritium fusion power plant will have to endure serious punishment.
  • What's more, so far they haven't included the deuterium and tritium fuel in the capsule for the tests.
  • tritium is relatively short-lived and penetrates the body weakly through the air compared to other radioactive contaminants.
British Dictionary definitions for tritium


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
Word Origin
C20: New Latin, from Greek tritos third
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for tritium

1933, Modern Latin, from Greek tritos "third" (see third) + chemical suffix -ium.

Online Etymology Dictionary, © 2010 Douglas Harper
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tritium in Medicine

tritium trit·i·um (trĭt'ē-əm, trĭsh'ē-)
Symbol T
A rare radioactive hydrogen isotope with atomic mass 3 and half-life 12.5 years, prepared artificially for use as a tracer and as a constituent of hydrogen bombs. Also called hydrogen-3.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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tritium in Science
  (trĭt'ē-əm, trĭsh'ē-əm)   
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. See more at hydrogen.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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