uranium

noun

ura·​ni·​um yu̇-ˈrā-nē-əm How to pronounce uranium (audio)
often attributive
: 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
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Uranium is another weak spot: five EU nations, including Finland, are still importing Russian uranium to fuel their nuclear plants. Katya Soldak, Forbes.com, 4 July 2025 The fund has also supported new nuclear industry companies in Anderson and Roane counties, including a $6 million grant for Orano USA in Oak Ridge to construct a state-of-the-art centrifuge uranium enrichment facility, creating 300 new jobs. Vivian Jones, The Tennessean, 2 July 2025 The presence of trucks before the attacks has raised questions about whether any enriched uranium or centrifuges had been spirited away before the attack, something repeatedly claimed by Iranian officials. Arkansas Online, 2 July 2025 The country began enriching uranium to higher levels after US President Donald Trump withdrew in 2018 from a nuclear agreement signed between the Obama administration and Iran. Mostafa Salem, CNN Money, 2 July 2025 See All Example Sentences for uranium

Word History

Etymology

New Latin, from Uranus

First Known Use

1790, in the meaning defined above

Time Traveler
The first known use of uranium was in 1790

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Cite this Entry

“Uranium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/uranium. Accessed 11 Jul. 2025.

Kids Definition

uranium

noun
ura·​ni·​um yȯ-ˈrā-nē-əm How to pronounce uranium (audio)
: a silvery heavy radioactive metallic element see element
Etymology

scientific Latin; named for the planet Uranus, from Latin Uranus, name of the god of heaven

Word Origin
The ancient Greek word ouranos meant "sky, heaven." It was fitting, then, for the Greeks to name their god of heaven Ouranos and their muse of astronomy Ourania. In Latin these names became Uranus and Urania. Uranus was the father of the god Saturn and the grandfather of Jupiter. In 1781 the English astronomer Sir William Herschel discovered by telescope the seventh planet of our solar system. It was the custom to name planets after Roman gods. Following this custom, the German astronomer Johann Bode suggested the name Uranus for this planet. It seemed a good idea since the fifth planet was called Jupiter and the sixth was Saturn. Eight years after the discovery of Uranus, the German chemist Martin Klaproth discovered a new element. He called it uranium after the new planet Uranus.

Medical Definition

uranium

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