noun, often attributive
ura·​ni·​um | \ yu̇-ˈrā-nē-əm \

Definition of uranium

: a silvery heavy radioactive polyvalent metallic element that is found especially in uraninite and exists naturally as a mixture of mostly nonfissionable isotopes — see Chemical Elements Table

Examples of uranium in a Sentence

Recent Examples on the Web

Each country had an extreme interest in the Congo's rich natural resources, particularly the uranium which could be used to further build nuclear weapons. David Grossman, Popular Mechanics, "That Time a CIA Spyplane Had to Dodge a Spear During the Cold War," 14 Jan. 2019 Trump has grown frustrated with Wray for what the president sees as his failure to investigate Clinton’s role in the Obama administration’s decision to allow the Russian nuclear agency to buy a uranium-mining company. Maggie Haberman, The Seattle Times, "Trump pushed for Justice Dept. prosecution of Clinton, Comey," 20 Nov. 2018 The drawing is at least 40,000 years old, based on uranium-series dating of a thin layer of rock deposited on top of the drawing since its creation. Kiona N. Smith, Ars Technica, "The world’s oldest figurative drawing depicts a wounded animal," 9 Nov. 2018 Work has begun on a new uranium processing facility, budgeted at $6.5 billion, slated to be the state’s largest construction project ever. Emily Strasser, Curbed, "A secret city opens up," 8 Aug. 2018 While working as a lobbyist, Wheeler worked, along with Interior Secretary Ryan Zinke, to open part of Utah’s Bears Ears National Monument for uranium mining. Brittany Shoot, Fortune, "Who Is Andrew Wheeler, Trump's New EPA Chief?," 5 July 2018 The Guptas, brothers who had holdings in everything from uranium mining to newspapers, maintained close ties with Jacob Zuma, the President of South Africa, and were notorious for having leveraged this connection for profit and influence. Ed Caesar, The New Yorker, "The Reputation-Laundering Firm That Ruined Its Own Reputation," 25 May 2018 The Saudis, however, have refused to rule out their right to enrich uranium, in part citing Iran’s ability to do so under the 2015 nuclear agreement world powers reached with Tehran, which the Trump administration pulled out of earlier this year. Michael R. Gordon, WSJ, "Lawmakers Want a Greater Say as U.S. Seeks a Saudi Nuclear Deal," 16 Dec. 2018 Mass spectrometer analysis shows how much of the trace uranium in the core’s layers has decayed to thorium, and the ratio between the two elements is used to calculate each layer’s approximate age. Elizabeth Svoboda, Scientific American, "Cores from Coral Reefs Hold Secrets of the Seas’ Past and Future," 6 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'uranium.' 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 uranium

circa 1797, in the meaning defined above

History and Etymology for uranium

New Latin, from Uranus

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Statistics for uranium

Last Updated

10 Feb 2019

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Time Traveler for uranium

The first known use of uranium was circa 1797

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More Definitions for uranium



English Language Learners Definition of uranium

: a radioactive element that is used to make nuclear energy and nuclear weapons


ura·​ni·​um | \ yu̇-ˈrā-nē-əm \

Kids Definition of uranium

: a radioactive metallic chemical element used as a source of atomic energy


ura·​ni·​um | \ yu̇-ˈrā-nē-əm \

Medical Definition of uranium

: a silvery heavy radioactive polyvalent metallic element that is found especially in pitchblende and uraninite and exists naturally as a mixture of three isotopes of mass number 234, 235, and 238 in the proportions of 0.006 percent, 0.71 percent, and 99.28 percent respectively symbol U — see Chemical Elements Table

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More from Merriam-Webster on uranium

Rhyming Dictionary: Words that rhyme with uranium

Spanish Central: Translation of uranium

Nglish: Translation of uranium for Spanish Speakers

Britannica English: Translation of uranium for Arabic Speakers

Britannica.com: Encyclopedia article about uranium

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