noun, often attributive
ura·​ni·​um | \ yu̇-ˈrā-nē-əm How to pronounce uranium (audio) \

Definition of uranium

: 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 In 2016, the first full year after Iran agreed to limits on uranium enrichment in exchange for sanctions relief, Iran’s economy roared back to life with a growth rate of 12.5 percent. Ian Bremmer, Time, 29 May 2021 They've been used to exploit any number of systems, from sabotaging Iran's uranium enrichment plants to affecting the credit ratings of hundreds of millions of people. Brian Greenberg, Forbes, 27 May 2021 In addition to setting back Iran’s uranium enrichment program, the attacks are likely to weaken Iran’s hand in indirect talks with the United States over restoring the 2015 nuclear agreement. New York Times, 20 Apr. 2021 In response to that killing, Iran boosted uranium enrichment to 20% purity. Scott Peterson, The Christian Science Monitor, 19 Apr. 2021 Natanz houses thousands of fast-spinning centrifuges, the machines at the core of the uranium enrichment process. Washington Post, 17 Apr. 2021 Iran is also using advanced centrifuges and making uranium metal, both banned under the deal. BostonGlobe.com, 9 Apr. 2021 More recently, in February, the International Atomic Energy Agency announced that Iran had produced uranium metal at one of its nuclear plants. The Editors, National Review, 7 Apr. 2021 Iran's production of uranium metal is a necessary step towards bomb-making, critics have said. Nick Paton Walsh, International Security Editor, CNN, 6 Apr. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'uranium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of uranium

circa 1797, in the meaning defined above

History and Etymology for uranium

New Latin, from Uranus

Keep scrolling for more

Learn More about uranium

Time Traveler for uranium

Time Traveler

The first known use of uranium was circa 1797

See more words from the same year

Statistics for uranium

Last Updated

2 Jun 2021

Cite this Entry

“Uranium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/uranium. Accessed 13 Jun. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

Keep scrolling for more

More Definitions for uranium



English Language Learners Definition of uranium

: a radioactive element that is used to make nuclear energy and nuclear weapons


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

Kids Definition of uranium

: a radioactive metallic chemical element used as a source of atomic energy


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

Medical Definition of uranium

: 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

More from Merriam-Webster on uranium

Nglish: Translation of uranium for Spanish Speakers

Britannica English: Translation of uranium for Arabic Speakers

Britannica.com: Encyclopedia article about uranium


Test Your Vocabulary

Name that Thing: Dog Breeds

Spell It

Can you spell these 10 commonly misspelled words?

 AlphaBear 2

Spell words. Make bears.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!