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: a metallic chemical element that is the most electropositive element known and that is used in photoelectric cells, in atomic clocks, and as a component of drilling fluid see Chemical Elements Table
Examples of cesium in a Sentence
Recent Examples on the Web
Germanium semiconductor detectors, radioactive cesium concentration detectors, sodium iodide scintillation spectrometers and more scan the produce for any signs of radioactivity.
—Kate Graham-Shaw, Scientific American, 9 Oct. 2024
An array of radioactive substances had been released during the disaster, including plutonium and uranium, but scientists were also on the lookout for harmful levels of radioactive cesium and iodine isotopes, which turned out to be the abundant and far-reaching contaminants of agricultural land.
—Kate Graham-Shaw, Scientific American, 9 Oct. 2024
The current gold standard for ultra-precise timekeeping is the cesium atomic clock, where the tiny and fixed energy transitions of the atom’s electrons are used to keep track of time.
—Shi En Kim, Smithsonian Magazine, 23 Sep. 2024
Scientists use a laser to bathe a cesium atom with photons.
—Quanta Magazine, 4 Sep. 2024
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Word History
Etymology
New Latin, from Latin caesius bluish gray
First Known Use
1861, in the meaning defined above
Dictionary Entries Near cesium
Cite this Entry
“Cesium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cesium. Accessed 24 Nov. 2024.
Kids Definition
Medical Definition
cesium
noun
ce·si·um
variants
or chiefly British caesium
: a silver-white soft ductile element of the alkali metal group that is the most electropositive element known and that is used especially in photoelectric cells
—symbol Cs
see Chemical Elements Table
More from Merriam-Webster on cesium
Nglish: Translation of cesium for Spanish Speakers
Britannica.com: Encyclopedia article about cesium
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