tho·​ri·​um | \ ˈthȯr-ē-əm How to pronounce thorium (audio) \

Definition of thorium

: a radioactive metallic element that is obtained especially from monazite and is usually associated with rare earths — see Chemical Elements Table

Examples of thorium in a Sentence

Recent Examples on the Web The country is also believed to have large deposits of thorium within its borders, but comparatively little uranium. Wired, "Andrew Yang Wants a Thorium Reactor by 2027. Good Luck, Buddy," 21 Oct. 2019 Using an instrument called an electrometer, built by Pierre and his brother, Marie measured the mysterious rays emitted by thorium and uranium. Adam Hadhazy, Discover Magazine, "The Top 10 Science Experiments of All Time," 10 Oct. 2019 But thorium would play an important role in Rona’s later career. New York Times, "Overlooked No More: Elizabeth Rona, Pioneering Scientist Amid Dangers of War," 28 Aug. 2019 But a thorium plant would be different than the plants with which Americans are familiar. David Grossman, Popular Mechanics, "Andrew Yang Wants Thorium Nuclear Power. Here's What That Means.," 27 Aug. 2019 By comparing the ratios of specific helium, thorium and uranium isotopes in each mineral sample, the researchers calculated approximately how long ago the zircon crystals solidified and started to decay. Fox News, "America's largest asteroid impact left a trail of destruction across the eastern US," 16 Aug. 2019 The substance turned out to be an isotope of the naturally occurring radioactive metal thorium, which had already been well studied. New York Times, "Overlooked No More: Elizabeth Rona, Pioneering Scientist Amid Dangers of War," 28 Aug. 2019 In contrast to his Democratic rivals calling for a turn away from nuclear power, Yang calls for increasing investment in nuclear energy by mining thorium (not uranium used in nuclear weapons). NBC News, "Andrew Yang picks climate change plan for his first major policy speech," 27 Aug. 2019 Searches had been made about how to poison a well and about uranium thorium fusion bombs, the search warrant affidavit said. Kirk Mitchell, The Denver Post, "Boulder porn suspect researched bombs, poisons, mass killers and found addresses for Denver area synagogues and mosques," 8 Aug. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'thorium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of thorium

1832, in the meaning defined above

History and Etymology for thorium

New Latin, from Old Norse Thōrr Thor

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Time Traveler for thorium

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The first known use of thorium was in 1832

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Last Updated

26 Nov 2019

Cite this Entry

“Thorium.” The Dictionary, Merriam-Webster Inc., Accessed 7 December 2019.

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tho·​ri·​um | \ ˈthōr-ē-əm, ˈthȯr- How to pronounce thorium (audio) \

Medical Definition of thorium

: a radioactive metallic element that occurs combined in minerals and is usually associated with rare earths symbol Th — see Chemical Elements Table

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