ac·​ti·​nide ˈak-tə-ˌnīd How to pronounce actinide (audio)
: 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 The lanthanide and actinide series — those two rows floating by themselves, named after their first members, lanthanum and actinium — are isolated like that as a concession to limited space. Bill Andrews, Discover Magazine, 26 June 2019 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 examples are programmatically compiled from various online sources to illustrate current usage of the word 'actinide.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


acti(nium) + (lantha)nide

First Known Use

1945, in the meaning defined above

Time Traveler
The first known use of actinide was in 1945

Dictionary Entries Near actinide

Cite this Entry

“Actinide.” Dictionary, Merriam-Webster, Accessed 6 Dec. 2023.

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