uranium
noun
ura·ni·um
yu̇-ˈrā-nē-əm 
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
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This, in turn, is expected to reduce the thermal expansion of the uranium-plutonium fuel pellet.
—
Aman Tripathi, Interesting Engineering, 18 Sep. 2025
Roughly 40% of the world’s uranium enrichment capacity belongs to Russia, leaving American utilities exposed to rising geopolitical tension.
—Ken Silverstein, Forbes.com, 17 Sep. 2025
Land Rover invited us to drive it the way it was intended—hard, fast, and on gnarly trails where cell service is as scarce as the uranium once mined from these hills.
—Kevin Sintumuang, Outside, 12 Sep. 2025
The dating technique used on the eggs, known more formally as carbonate uranium-lead, or U-Pb, dating, is a common process for determining the age of carbonate minerals — those containing calcium, iron, manganese and magnesium.
—Mindy Weisberger, CNN Money, 12 Sep. 2025
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Aman Tripathi, Interesting Engineering, 18 Sep. 2025
Roughly 40% of the world’s uranium enrichment capacity belongs to Russia, leaving American utilities exposed to rising geopolitical tension.
—Ken Silverstein, Forbes.com, 17 Sep. 2025
Land Rover invited us to drive it the way it was intended—hard, fast, and on gnarly trails where cell service is as scarce as the uranium once mined from these hills.
—Kevin Sintumuang, Outside, 12 Sep. 2025
The dating technique used on the eggs, known more formally as carbonate uranium-lead, or U-Pb, dating, is a common process for determining the age of carbonate minerals — those containing calcium, iron, manganese and magnesium.
—Mindy Weisberger, CNN Money, 12 Sep. 2025
See All Example Sentences for uranium
Cite this Entry
“Uranium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/uranium. Accessed 24 Sep. 2025.
Copy CitationKids Definition
uranium
noun
ura·ni·um
yȯ-ˈrā-nē-əm
: 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
: 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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