noun ·Uncommon ·Advanced level

Definitions

Noun

1. 1
   The chemical element (symbol Cs) with an atomic number of 55. It is a soft, gold-colored, highly reactive alkali metal. uncountable
2. 2
   a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal wordnet

Synonyms

All synonyms

atomic number 55cesiumcesiumcs

Example

More examples

"Lithium, sodium, potassium, rubidium, caesium and francium are alkali metals."

Etymology

From Latin caesius (“sky-blue”), in reference to the radiation spectra, + -ium.

Related phrases

caesium auridecaesium azidecaesium cellcaesium chloridecaesium clockcaesium fluoridecaesium hydroxidecaesium iodidecaesium nitratecaesium-137cesium auridecesium azide

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.