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

Recent Examples on the Web

Iran boosted its stockpile of uranium enriched close to weapons-grade levels just before Israel launched its June 13 military assault, the United Nations nuclear watchdog said in a confidential report obtained by the Associated Press (AP) on Wednesday. —Jenna Sundel gabe Whisnant, MSNBC Newsweek, 3 Sep. 2025

Instead of splitting heavy atoms like uranium or plutonium to release energy, fusion works by fusing hydrogen atoms to form helium for energy. —New Atlas, 2 Sep. 2025

The net result is that the uranium market could be hit by a 20-million-pound decline on earlier supply forecasts. —Tim Treadgold, Forbes.com, 2 Sep. 2025

The move, which Iran said lacked legal basis, stokes tensions two months after the US bombed Iranian uranium enrichment sites, stalling nuclear talks with the US; the Europeans had set an end-of-August deadline for progress in negotiations. —semafor.com, 1 Sep. 2025

Word History

Etymology

New Latin, from Uranus

First Known Use

1790, in the meaning defined above

Phrases Containing uranium

• uranium hexafluoride

Rhymes for uranium

• geranium
• germanium
• titanium
• cranium
• transuranium

Kids 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