actinium

noun
ac·​tin·​i·​um | \ ak-ˈti-nē-əm How to pronounce actinium (audio) \

Definition of actinium

: a radioactive trivalent metallic element that resembles lanthanum in chemical properties and that is found especially in pitchblende — see Chemical Elements Table

Examples of actinium in a Sentence

Recent Examples on the Web Other theorists have predicted that hydrides such as calcium hydride or actinium hydride should superconduct at close to room temperature—and at a pressure considerably less than that needed for CSH. Robert F. Service, Science | AAAS, 26 Aug. 2021

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

First Known Use of actinium

1900, in the meaning defined above

History and Etymology for actinium

borrowed from French, from Greek aktīn-, aktís "ray, beam" + -ium -ium; so called from its radioactivity — more at actin-

Keep scrolling for more

Learn More About actinium

Time Traveler for actinium

Time Traveler

The first known use of actinium was in 1900

See more words from the same year

Dictionary Entries Near actinium

Actinistia

actinium

actinium emanation

See More Nearby Entries 

Statistics for actinium

Last Updated

8 Sep 2021

Cite this Entry

“Actinium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/actinium. Accessed 20 Sep. 2021.

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

Keep scrolling for more

More Definitions for actinium

actinium

noun
ac·​tin·​i·​um | \ ak-ˈtin-ē-əm How to pronounce actinium (audio) \

Medical Definition of actinium

: a radioactive trivalent metallic element that resembles lanthanum in chemical properties and that is found especially in pitchblende symbol Ac — see Chemical Elements Table

More from Merriam-Webster on actinium

Britannica.com: Encyclopedia article about actinium

WORD OF THE DAY

Test Your Vocabulary

Farm Idioms Quiz

  • cow coming home
  • What does 'poke' refer to in the expression 'pig in a poke'?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

TAKE THE QUIZ
 AlphaBear 2

Spell words. Make bears.

TAKE THE QUIZ
Love words? Need even more definitions?

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