casein
/ˈkeɪ.siːn/
"casein" is a 6-letter English headword indexed on PlainSpell.
The verdict
“casein” is uncommon English (frequency #50,416 among 43,570 “C” headwords), classed as a noun. The kind of spelling people second-guess.
- #50,416
- frequency rank, English
- 43,570
- “C” headwords
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - A protein present in both milk and in the seeds of leguminous plants.
| Property | Value |
|---|---|
| Headword | casein |
| Language | English |
| Part of speech | Noun |
| IPA | /ˈkeɪ.siːn/ |
| Letters | 6 |
| Frequency rank | #50,416 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “casein” sits in English frequency
Rare enough to double-check
casein is uncommon English at frequency #50,416 among 43,570 “C” headwords, classed as anoun, transcribed /ˈkeɪ.siːn/. Rarity is why readers land here mid-draft. Gloss: "A protein present in both milk and in the seeds of leguminous plants.".
The misspelling generator found no plausible variants for casein, typically a sign the spelling maps closely to how the word sounds. Our confusable-pair dataset has no match for it, since nothing in our dataset looks or sounds close enough to cause mix-ups.
Etymologically, the entry records: From French caséine, formed from Latin cāseus (“cheese”) + -ine. The correct English form is casein, spelled C-A-S-E-I-N.
Definition
- 1A protein present in both milk and in the seeds of leguminous plants.
Etymology
From French caséine, formed from Latin cāseus (“cheese”) + -ine.
Synonyms
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.
Frequently Asked Questions
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Using “casein”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is C-A-S-E-I-N - every other letter order is a misspelling in standard orthography.
- Say it as /ˈkeɪ.siːn/ (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.