noun, often attributive
ura·​ni·​um | \ yu̇-ˈrā-nē-əm How to pronounce uranium (audio) \

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 The administration has been negotiating with Tehran a return to an Obama-era nuclear agreement that Mr. Trump dismantled, which led to Iran’s accelerating its uranium enrichment. New York Times, 24 July 2022 Former president Donald Trump had needlessly wrecked the Iran nuclear deal, reimposing sanctions that goaded Tehran to rev up uranium enrichment and inch closer toward the unthinkable: the capacity to produce an atomic weapon. Ishaan Tharoor, Washington Post, 14 July 2022 The ins and outs of centrifuge production and rotation, levels of uranium enrichment and the fine points of inspection rights are details that were never destined to hold the attention of the masses, for the duration. Amy Kellogg, Fox News, 11 July 2022 If the controller appeared to be operating a uranium enrichment centrifuge, files were transferred and the operations of that manufacturing process went subtly askew. Greg Autry, Forbes, 27 June 2022 With the negotiations stalled, Iran's nuclear capabilities, including its uranium enrichment level, signal the country is the closest its ever been to making a nuclear weapon, experts warn. Somayeh Malekian, ABC News, 21 June 2022 Israel's assassinations in recent years of top officials -- including a pre-eminent nuclear scientist -- have also failed to curb Iran's uranium enrichment. Tamara Qiblawi, CNN, 12 June 2022 Rather than destroy a uranium-enrichment plant, U.S. leaders would timidly beg the rogue nation to stop. WSJ, 9 June 2022 Biden favors a return to a 2015 pact — negotiated by the Obama administration and dumped by President Trump — that sought to constrain Iran’s ability to enrich uranium. Noah Biermanstaff Writer, Los Angeles Times, 14 July 2022 See More

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.

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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Time Traveler for uranium

Time Traveler

The first known use of uranium was circa 1797

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Dictionary Entries Near uranium



uranium 235

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Statistics for uranium

Last Updated

1 Aug 2022

Cite this Entry

“Uranium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/uranium. Accessed 8 Aug. 2022.

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More Definitions for uranium


ura·​ni·​um | \ yu̇-ˈrā-nē-əm How to pronounce uranium (audio) \

Kids Definition of uranium

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


ura·​ni·​um | \ yu̇-ˈrā-nē-əm How to pronounce uranium (audio) \

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

More from Merriam-Webster on 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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