[Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/dictionaries/school/w/caesium.html)

[home](https://md.mova.elamur.ai/free/en/) / [dictionaries](https://md.mova.elamur.ai/free/en/dictionaries/) / [The school dictionary](https://md.mova.elamur.ai/free/en/dictionaries/school/) / caesium

[← C](https://md.mova.elamur.ai/free/en/dictionaries/school/C/)

# caesium

«caesium» in Mova's school dictionary: **a soft, silvery-gold metal, a chemical element (symbol…** — its meaning for a pupil, its sense in the lessons and examples.

### part of speech

noun (caesium — uncountable)

### meaning for a pupil

1) Caesium is a soft, silvery-gold metal, a chemical element (symbol Cs) that reacts violently with water. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/#m1)

2) Caesium is used in atomic clocks, the most accurate clocks there are. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/#m2)

### sense in the lessons

In science lessons on elements and the periodic table (group 1 alkali metals with sodium and potassium); in maths and science, time: the second is defined using caesium atoms; in news about nuclear accidents, radioactive caesium.

### examples

- Caesium explodes if you drop it into water. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/#x1)
- Atomic clocks use caesium to keep perfect time. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/#x2)
- Caesium's symbol is Cs. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/#x3)
- Caesium melts on a very hot day. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/#x4)
- Radioactive caesium spread after the nuclear accident. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/#x5)

### note

UK spelling «caesium»; US spelling «cesium». Uncountable. Say it «SEE-zee-um». Safety: alkali metals are dangerous and only handled by trained scientists.

### Trees and pragmatics

[Every meaning and example of «caesium» parsed by Mova](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/C/caesium/), each sentence with its dependency tree and frames.