cofactor

noun

By · According to Wiktionary data (CC BY-SA) ·

"cofactor" is a 8-letter English headword indexed on PlainSpell.

The verdict

“cofactor” is uncommon English (frequency #73,079 among 43,570 “C” headwords), classed as a noun. The kind of spelling people second-guess.

#73,079
frequency rank, English
43,570
“C” headwords

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - A contributing factor.

Key facts for cofactor
PropertyValue
Headwordcofactor
LanguageEnglish
Part of speechNoun
Letters8
Frequency rank#73,079
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Where “cofactor” sits in English frequency

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right). cofactor lands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

Rare enough to double-check

cofactor is uncommon English at frequency #73,079 among 43,570 “C” headwords, classed as anoun. Rarity is why readers land here mid-draft. 5 senses are on record.

Zero misspellings are on record for cofactor in our index, and the word's spelling is regular enough that our generator found nothing worth flagging. It is not paired with a close-neighbour confusable in our dataset, since no other headword is close enough in sound or shape to pair with it.

Etymologically, the entry records: From co- + factor. The correct English form is cofactor, spelled C-O-F-A-C-T-O-R.

Definition

  1. 1
    A contributing factor.
  2. 2
    A substance, especially a coenzyme or a metal, that must be present for an enzyme to function.
  3. 3
    A molecule that binds to and regulates the activity of a protein.
  4. 4
    The result of a number being divided by one of its factors.
  5. 5
    The signed determinant of the submatrix produced by removing the row and column containing a specified element; primarily used in the recursive definition and calculation of the determinant of a matrix.

Etymology

From co- + factor.

Synonyms

minor

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

How do you spell "cofactor"?
"cofactor" is spelled C-O-F-A-C-T-O-R.
What does "cofactor" mean?
As a noun, "cofactor" means: A contributing factor.
What is the origin of the word "cofactor"?
From co- + factor. 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.

Using “cofactor”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is C-O-F-A-C-T-O-R - every other letter order is a misspelling in standard orthography.
  • 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.

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

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list