noun
- a soft, silvery-white metallic chemical element that is highly reactive and used in atomic clocks and photoelectric cells
Usage: chemistry; also spelled cesium in American English
Examples
- Caesium is the most electropositive of all elements.
- The atomic clock uses caesium atoms to measure time with extreme precision.
- Caesium ignites spontaneously when exposed to air.
- Scientists extracted caesium from the mineral pollucite.
- The photoelectric cell contains a small amount of caesium.
- Caesium has the atomic number 55 on the periodic table.