am·​er·​i·​ci·​um | \ ˌa-mə-ˈri-shē-əm How to pronounce americium (audio) , -sē- \

Definition of americium

: a radioactive metallic element produced artificially by bombarding plutonium with high-energy neutrons — see Chemical Elements Table

Examples of americium in a Sentence

Recent Examples on the Web The most stable isotopes of americium and curium decay faster than uranium’s most stable isotopes. Scientific American, 1 Apr. 2022 In Colorado, for instance, 27 buildings house scary-sounding elements such as cesium 137, cobalt 60, americium 241 and iridium 192. Sarah Scoles, Scientific American, 11 Mar. 2022 Many other toxic and radioactive contaminants have also been found at Rocky Flats in addition to plutonium: americium, uranium, cadmium, PCBs, beryllium, and more. Longreads, 10 Aug. 2020 Readings for contaminants like uranium and americium were also found to be well below the threshold for health concerns, the report concluded. John Aguilar, The Denver Post, 6 Sep. 2019 Engineering Analytics will specifically be measuring for plutonium, americium and uranium and seeing whether levels of the radionuclides are a hazard to human health. John Aguilar, The Denver Post, 2 July 2019 The waste includes isotopes of iodine, strontium, americium, plutonium, uranium and other unstable elements, many of which are toxic as well as radioactive. Ralph Vartabedian,, 5 June 2019 Inhalation of the particles, which included uranium, thorium, plutonium and americium, can increase the risk of cancer. Hal Bernton, The Seattle Times, 14 June 2018 Heavier elements are also created in a reactor core when uranium that hasn't been fissioned captures neutrons (plutonium and americium are two of these). Andrew Karam, Popular Mechanics, 11 Mar. 2016 See More

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

First Known Use of americium

1946, in the meaning defined above

History and Etymology for americium

New Latin, from America + New Latin -ium

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Time Traveler for americium

Time Traveler

The first known use of americium was in 1946

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Dictionary Entries Near americium

American yew



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Statistics for americium

Last Updated

13 Apr 2022

Cite this Entry

“Americium.” Dictionary, Merriam-Webster, Accessed 18 May. 2022.

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More Definitions for americium


am·​er·​i·​ci·​um | \ ˌam-ə-ˈris(h)-ē-əm How to pronounce americium (audio) \

Medical Definition of americium

: a radioactive metallic element produced by bombardment of plutonium with high-energy neutrons symbol Am — see Chemical Elements Table

More from Merriam-Webster on americium Encyclopedia article about americium


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