Standard Lemma guide

caesium

noun · 2 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

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  • sē'zēəm
  • /ˈsiːzi.əm/
  • General-American: Recorded audio is listed in the source snapshot.
  • US: Recorded audio is listed in the source snapshot.

1

noun

Meaning 1

The chemical element (symbol Cs) with an atomic number of 55. It is a soft, gold-colored, highly reactive alkali metal.

Definition source: English Wiktionary via Wiktextract

Usage: uncountable

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

noun

Meaning 2

a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal

Definition source: Princeton WordNet 3.0

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: cesium, Cs, atomic number 55

Antonyms: none provided

Broader terms: metallic element, metal

Narrower terms: cesium 137

History

Etymology

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

Across languages

Translations

81 source translations are retained for this English entry.

  • Afrikaans: sesium — a metallic chemical element
  • Albanian: cezium — a metallic chemical element
  • Arabic: سِيزِيُوم (sīziyūm) — a metallic chemical element
  • Armenian: ցեզիում (cʻezium) — a metallic chemical element
  • Asturian: cesiu — a metallic chemical element
  • Basque: zesioa — a metallic chemical element
  • Belarusian: цэ́зій (cézij) — a metallic chemical element
  • Breton: seziom — a metallic chemical element
  • Bulgarian: це́зий (cézij) — a metallic chemical element
  • Catalan: cesi — a metallic chemical element
  • Chinese Mandarin: 銫 /铯 (sè) — a metallic chemical element
  • Cornish: cesiom — a metallic chemical element
  • Czech: cezium — a metallic chemical element
  • Czech: cesium — a metallic chemical element
  • Danish: cæsium — a metallic chemical element
  • Dutch: cesium — a metallic chemical element
  • Esperanto: cezio — a metallic chemical element
  • Estonian: tseesium — a metallic chemical element
  • Faroese: sesium — a metallic chemical element
  • Finnish: cesium — a metallic chemical element
  • French: césium — a metallic chemical element
  • French: cæsium — a metallic chemical element
  • West-Frisian: cesium — a metallic chemical element
  • Friulian: cesi — a metallic chemical element
  • Galician: cesio — a metallic chemical element
  • Georgian: ცეზიუმი (ceziumi) — a metallic chemical element
  • German: Cäsium — a metallic chemical element
  • German: Zäsium — a metallic chemical element
  • Greek: καίσιο (kaísio) — a metallic chemical element
  • Hebrew: צסיום (tsesyum) — a metallic chemical element
  • Hebrew: צזיום (tsezyum) — a metallic chemical element
  • Hindi: द्युतातु (dyutātu) — a metallic chemical element
  • Hungarian: cézium — a metallic chemical element
  • Icelandic: sesín — a metallic chemical element
  • Indonesian: sesium — a metallic chemical element
  • Irish: caeisiam — a metallic chemical element
  • Italian: cesio — a metallic chemical element
  • Japanese: セシウム (seshiumu) — a metallic chemical element
  • Kashubian: céz — a metallic chemical element
  • Kazakh: цезий (sezii) — a metallic chemical element
  • Korean: 세슘 (sesyum) — a metallic chemical element
  • Latin: caesium — a metallic chemical element
  • Latvian: cēzijs — a metallic chemical element
  • Lithuanian: cezis — a metallic chemical element
  • Luxembourgish: Zäsium — a metallic chemical element
  • Macedonian: цезиум (cezium) — a metallic chemical element
  • Malay: sesium — a metallic chemical element
  • Maltese: ċesju — a metallic chemical element
  • Manx: kaishum — a metallic chemical element
  • Mongolian: цези (cezi) — a metallic chemical element
  • Norwegian Bokmål: cesium — a metallic chemical element
  • Norwegian Nynorsk: cesium — a metallic chemical element
  • Occitan: cèsi — a metallic chemical element
  • Persian: سزیم (seziyom) — a metallic chemical element
  • Polish: cez — a metallic chemical element
  • Portuguese: césio — a metallic chemical element
  • Punjabi: ਸੀਜ਼ੀਅਮ (sīzīama) — a metallic chemical element
  • Romanian: cesiu — a metallic chemical element
  • Russian: це́зий (cézij) — a metallic chemical element
  • Scottish Gaelic: caesium — a metallic chemical element
  • Serbo-Croatian: це̑зиј — a metallic chemical element
  • Serbo-Croatian: цезиjум — a metallic chemical element
  • Serbo-Croatian: cȇzij — a metallic chemical element
  • Serbo-Croatian: cezijum — a metallic chemical element
  • Slovak: cézium — a metallic chemical element
  • Slovene: cẹ́zij — a metallic chemical element
  • Spanish: cesio — a metallic chemical element
  • Swedish: cesium — a metallic chemical element
  • Tagalog: sesyo — a metallic chemical element
  • Tajik: сезий (seziy) — a metallic chemical element
  • Tamil: சீரிலியம் (cīriliyam) — a metallic chemical element
  • Thai: ซีเซียม (sii-sîiam) — a metallic chemical element
  • Turkish: sezyum — a metallic chemical element
  • Ukrainian: це́зій (cézij) — a metallic chemical element
  • Uyghur: سېزىي (sëziy) — a metallic chemical element
  • Uzbek: цезий — a metallic chemical element
  • Uzbek: tseziy — a metallic chemical element
  • Vietnamese: xezi — a metallic chemical element
  • Vietnamese: xêzi — a metallic chemical element
  • Volapük: zäsin — a metallic chemical element
  • Welsh: cesiwm — a metallic chemical element