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

The country has continued to operate facilities that produce plutonium and highly enriched uranium, according to three Stanford University researchers. Andrew Jeong, WSJ, "North Korea Keeps Stockpiling Materials to Make Nuclear Weapons, Report Finds," 12 Feb. 2019 Hillary Clinton's alleged role in the sale of a uranium enterprise to a Russian company was a campaign allegation, but Trump repeatedly raised it again as the Mueller investigation continued. Glenn Kessler, chicagotribune.com, "Trump's 'spygate' claim is latest off-target salvo at Russia probe," 2 June 2018 In many communities, people drink, shower, cook and wash dishes with water containing excessive amounts of pollutants, including arsenic, nitrates and uranium. Dale Kasler, Phillip Reese And Ryan Sabalow, sacbee, "360,000 Californians have unsafe drinking water. Are you one of them?," 1 June 2018 Photo: Getty North Korea is still using a uranium-enrichment facility at the heart of last week’s summit between President Trump and North Korean leader Kim Jong Un, the United Nations atomic agency said. Michael R. Gordon, WSJ, "North Korea Still Using Uranium-Enrichment Facility, U.N. Agency Says," 4 Mar. 2019 That's where the North has a plutonium reactor and a uranium enrichment facility that can produce fissile material for atomic bombs. Matthew Pennington, Fox News, "North Korea's offer of concessions comes with a catch for US," 20 Sep. 2018 But the law doesn’t bar a country from using the program to enrich and reprocess uranium to make a bomb. Alex Ward, Vox, "Exclusive: House Democrat to introduce new bill punishing Saudi Arabia over Khashoggi," 9 Nov. 2018 The scars from such a collision, says Mojzsis, have been left on uranium and lead isotopes. Jill Kiedaisch, Popular Mechanics, "Life on Earth May Have Been Born From a Maelstrom of Molten Iron," 15 Jan. 2019 Madagascar is one of the world’s poorest nations despite having reserves of nickel, cobalt, gold, uranium and other minerals. Fox News, "US diplomat in Madagascar found dead in home, suspect in custody," 26 Sep. 2018

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

Statistics for uranium

Last Updated

5 May 2019

Look-up Popularity

Time Traveler for uranium

The first known use of uranium was circa 1797

See more words from the same year

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

Keep scrolling for more

More from Merriam-Webster on uranium

Rhyming Dictionary: Words that rhyme with uranium

Spanish Central: Translation of uranium

Nglish: Translation of uranium for Spanish Speakers

Britannica English: Translation of uranium for Arabic Speakers

Britannica.com: Encyclopedia article about uranium

Comments on uranium

What made you want to look up uranium? Please tell us where you read or heard it (including the quote, if possible).


something valued as if it were money

Get Word of the Day daily email!

Test Your Vocabulary

Time Traveler Quiz: Which Word Came First?

  • time traveler quiz which word came first
  • Which came first?
True or False

Test your knowledge - and maybe learn something along the way.

Bee Cubed

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

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