ac·​ti·​nide | \ ˈak-tə-ˌnīd How to pronounce actinide (audio) \

Definition of actinide

: any of the series of elements with increasing atomic numbers that begins with actinium or thorium and ends with lawrencium — see Periodic Table

Examples of actinide in a Sentence

Recent Examples on the Web After 200 years, the decay heat of HLW would be reduced by a factor of up to 30 in all minor actinide-burning schemes as compared to the reference PWR once- through scheme. James Conca, Forbes, 27 Apr. 2021 Meant for studying actinides, the ROBL allows scientists to analyze the metals with an extremely close eye through spectroscopy. David Grossman, Popular Mechanics, 22 Oct. 2019 To form their artificial actinides, the team wanted to make precursors. David Grossman, Popular Mechanics, 22 Oct. 2019 Uranium is currently the actinide of choice for the industry, used (sometimes with a little plutonium) in 100 percent of the world’s commercial reactors. Richard Martin, WIRED, 21 Dec. 2009

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

Keep scrolling for more

First Known Use of actinide

1945, in the meaning defined above

History and Etymology for actinide

acti(nium) + (lantha)nide

Keep scrolling for more

Learn More About actinide

Time Traveler for actinide

Time Traveler

The first known use of actinide was in 1945

See more words from the same year

Dictionary Entries Near actinide

actinic glass


actinide series

See More Nearby Entries 

Statistics for actinide

Cite this Entry

“Actinide.” Dictionary, Merriam-Webster, Accessed 19 May. 2022.

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

More from Merriam-Webster on actinide Encyclopedia article about actinide


Test Your Vocabulary

Great Words for Scrabble

  • scrabble tiles that read scrabble quiz
  • Which of the following Q-without-U words means the number five in cards or dice?
Spell It

Can you spell these 10 commonly misspelled words?

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

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