caesium
/ˈsiːzi.əm/
"caesium" is a 7-letter English headword indexed on PlainSpell.
The verdict
“caesium” is uncommon English (frequency #75,696 among 43,570 “C” headwords), classed as a noun. The kind of spelling people second-guess.
- #75,696
- frequency rank, English
- 43,570
- “C” headwords
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - The chemical element (symbol Cs) with an atomic number of 55. It is a soft, gold-colored, highly reactive alkali metal.
| Property | Value |
|---|---|
| Headword | caesium |
| Language | English |
| Part of speech | Noun |
| IPA | /ˈsiːzi.əm/ |
| Letters | 7 |
| Frequency rank | #75,696 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “caesium” sits in English frequency
Rare enough to double-check
caesium is uncommon English at frequency #75,696 among 43,570 “C” headwords, classed as anoun, transcribed /ˈsiːzi.əm/. Rarity is why readers land here mid-draft. Gloss: "The chemical element (symbol Cs) with an atomic number of 55. It is a soft, gold-colored, highly reactive alkali metal.".
The misspelling generator found no plausible variants for caesium, a sign its spelling follows regular English conventions. No close-neighbour confusable shows up for this headword in our dataset, which typically means the spelling is too distinctive to be mistaken for another word.
Etymologically, the entry records: From Latin caesius (“sky-blue”), in reference to the radiation spectra, + -ium. The correct English form is caesium, spelled C-A-E-S-I-U-M.
Definition
- 1The chemical element (symbol Cs) with an atomic number of 55. It is a soft, gold-colored, highly reactive alkali metal.
Etymology
From Latin caesius (“sky-blue”), in reference to the radiation spectra, + -ium.
This word in other languages
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.
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Using “caesium”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is C-A-E-S-I-U-M - every other letter order is a misspelling in standard orthography.
- Say it as /ˈsiːzi.əm/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
- Browse more English words and confusable pairs in the same reference. English words
Other uncommon English words near this rank
Data Source
Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.