cilium

/ˈsɪl.i.əm/

//ˈsɪl.i.əm// noun

"cilium" is a 6-letter English headword indexed on PlainSpell.

The verdict

“cilium” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.

Unranked
below top-frequency English
6
letters

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - A short microscopic hairlike organelle projecting from a eukaryotic cell (such as a unicellular organism or one cell of a multicelled organism) which serve either for propulsion by causing currents...

Corpus desk

Index EN-cilium · cilium · English

cilium · unranked · 0 variants · 0 confusables

  • FREQ-UNRANKED Unranked
  • LEN-LONG 6 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-THIN "C" thin
  • PHOTO-UNK Peer pending

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Key facts for cilium
PropertyValue
Headwordcilium
LanguageEnglish
Part of speechNoun
IPA/ˈsɪl.i.əm/
Letters6
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “cilium” in English

ciliumsits beyond the 100,000 most-frequent English words, in the long tail of technical, archaic, or otherwise rare vocabulary where spelling doubt tends to strike hardest.

Beyond rank #100,000. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

cilium is uncommon English outside the top frequency list, classed as anoun, transcribed /ˈsɪl.i.əm/. Rarity is why readers land here mid-draft. 4 senses are on record.

We couldn't generate a plausible misspelling set for cilium, a sign its spelling follows regular English conventions. This entry stands alone in our confusable dataset, which usually means its spelling is distinct enough that readers don't reach for a similar-looking word instead.

Etymologically, the entry records: Borrowed from Latin cilium (“eyelid”). The correct English form is cilium, spelled C-I-L-I-U-M.

Definition

  1. 1
    A short microscopic hairlike organelle projecting from a eukaryotic cell (such as a unicellular organism or one cell of a multicelled organism) which serve either for propulsion by causing currents in the surrounding fluid or as sensors.
  2. 2
    One of the fine hairs along an insect's wing.
  3. 3
    One of the hairs or similar protrusions along the margin of an organ.
  4. 4
    An eyelash.

Recorded use

Wiktionary examples

These source excerpts show how cilium appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. It is the deeper parts of such cells which give rise to delicate muscular fibres or networks of fibres, while the superficially placed body of the cell myoblast), the part which produces the above, performs other functions, and usually bears a cilium.
  2. The clockwise beating of cilia results in a net flow of extraembryonic fluid leftwards […]

Etymology

Borrowed from Latin cilium (“eyelid”).

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). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "cilium"?
"cilium" is spelled C-I-L-I-U-M. The IPA pronunciation is /ˈsɪl.i.əm/.
What does "cilium" mean?
As a noun, "cilium" means: A short microscopic hairlike organelle projecting from a eukaryotic cell (such as a unicellular organism or one cell of a multicelled organism) which serve either for propulsion by causing currents...
How do you pronounce "cilium"?
The IPA (International Phonetic Alphabet) transcription for "cilium" is /ˈsɪl.i.əm/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "cilium"?
Borrowed from Latin cilium (“eyelid”). See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list