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English definition of “caesium”

caesium

noun [U] uk (US cesium)   /ˈsiː.zi.əm/ (symbol Cs) us  
a chemical element that is a soft silver-white alkaline metal, that reacts strongly with other chemicals and is used in photocellsChemical elements
(Definition of caesium from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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