Definition of "tritium" [trit•i•um]

• 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. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The worlds main source of tritium is Canada, Ontario actually."
• "The experiments also yielded a radioactive material called tritium, which is another product of fusion, Xu and Butt said."
• "Last July, months before most Vermonters had heard the word tritium, Gundersen was poring over a Nuclear Regulatory Commission report when a mention of underground pipes at Vermont Yankee caught his attention."