cesium

noun

ce·​si·​um ˈsē-zē-əm 

 also  -zhē-

: 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

Word History

Etymology

New Latin, from Latin caesius bluish gray

First Known Use

1861, in the meaning defined above

Kids Definition

cesium

noun

ce·​si·​um ˈsē-zē-əm 

: a silver-white soft element used especially in photoelectric cells see element

Medical Definition

cesium

noun

ce·​si·​um

variants or chiefly British caesium

ˈsē-zē-əm 

: 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