am·​er·​i·​ci·​um ˌa-mə-ˈri-shē-əm How to pronounce americium (audio)
: 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 Alternatively, Cotruvo suggests, captured americium and curium could be recycled back into nuclear fuel. Nikk Ogasa, Scientific American, 19 Nov. 2021 Along with americium, the discovery of curium was related to the top-secret Manhattan Project, so no announcement was made until WWII ended. Allison Futterman, Discover Magazine, 17 Sep. 2022 Some of those more obscure elements play fundamental roles in shaping modern-day society: lighter flints use cerium, smoke detectors have americium inside, and color televisions need Europium to function. Nathaniel Scharping, Discover Magazine, 7 Nov. 2016 The team created 30 atoms of element 115 by firing a beam of calcium atoms at a piece of americium foil. Shannon Palus, Discover Magazine, 19 Dec. 2013 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

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'americium.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


New Latin, from America + New Latin -ium

First Known Use

1946, in the meaning defined above

Time Traveler
The first known use of americium was in 1946

Dictionary Entries Near americium

Cite this Entry

“Americium.” Dictionary, Merriam-Webster, Accessed 23 Jul. 2024.

Kids Definition


am·​er·​i·​ci·​um ˌam-ə-ˈris-ē-əm How to pronounce americium (audio)
: a radioactive metallic element produced by bombardment of plutonium with high-energy neutrons see element

Medical Definition


am·​er·​i·​ci·​um ˌam-ə-ˈris(h)-ē-əm How to pronounce americium (audio)
: a radioactive metallic element produced by bombardment of plutonium with high-energy neutrons
symbol Am
see Chemical Elements Table

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