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

The fact that no country has ever enriched uranium to 60 percent, as Iran has, without building nuclear weapons is a reminder that getting Iran to abandon this path will be difficult. —Elliott Abrams, Foreign Affairs, 7 Feb. 2025

The program is rapidly advancing, with Tehran close to enriching uranium at weapons-grade levels. —Kristan Hawkins, Newsweek, 6 Feb. 2025

At stake are potentially billions of dollars withheld from Iran through crushing sanctions and the future of a program on the precipice of enriching weapons-grade uranium. —Nasser Karimi, Chicago Tribune, 5 Feb. 2025

The Head of the International Atomic Energy Agency (IAEA) told world leaders at the Davos World Economic Forum that Iran has roughly enough uranium, if enriched further, to develop nearly five nuclear weapons. —Caitlin McFall, Fox News, 22 Jan. 2025

Word History

Etymology

New Latin, from Uranus

First Known Use

1790, in the meaning defined above

Phrases Containing uranium

• uranium hexafluoride

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