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

While June’s Operation Midnight Hammer interrupted Iranian progress toward a larger nuclear stockpile, its existing stocks of 60% enriched uranium were merely weeks away from purification to weapons grade. —Chuck Devore, Chicago Tribune, 18 Mar. 2026

Its centrifuges for enriching more uranium, and parts for more centrifuges. —Matthew Bunn, The Conversation, 17 Mar. 2026

Presently, the United States and Israel are doing the right thing in militarily ending all possibilities that Iran will be able to continue weaponizing uranium and manufacturing long-range ballistic missiles. —Bill Keane, Hartford Courant, 15 Mar. 2026

The White House, however, has not revealed publicly or to Congress any evidence or intelligence showing that the uranium at the Tehran facility was intended for weapon development. —Ryan Mancini, The Hill, 11 Mar. 2026

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