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Definition of cesium

cesium

/ˈsiːziəm/
(UK: caesium)
ce · si · um
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cesium Lexical Profile

cesium Game Scores & Validity

• noun

1

American A soft, silvery-gold alkali metal chemical element with atomic number 55 (symbol Cs), notable for being liquid near room temperature, reacting violently with water, and serving as the frequency standard in atomic clocks.

Example

"Modern global positioning satellites rely on the extraordinarily precise oscillations of cesium atoms to maintain accurate timekeeping."

Synonyms
View all synonyms for cesium

Word Nuance & Usage

Spelled 'cesium' in American English and 'caesium' in British English and international IUPAC nomenclature.

• Rhymes for cesium

• Nearby Words

cesar
cesare
cesarean
cesium
cessation
cesspit
cesspool

Word Origin & Etymology

Coined in 1860 by German scientists Robert Bunsen and Gustav Kirchhoff from Latin 'caesius' ('bluish-gray' or 'sky-blue'), in reference to the bright blue lines in its emission spectrum.

Cite this Entry

Wordmom. (2026). Definition of Cesium. In Wordmom Dictionary. Retrieved Nov 5, 2026, from https://wordmom.com/dictionary/cesium
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