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 5,599 “C” headwords), classed as a noun. The kind of spelling people second-guess.

#73,079
frequency rank, English
5,599
“C” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - A contributing factor.

Corpus desk

Index EN-cofactor · cofactor · English

cofactor · rank #73,079 · 0 variants · 0 confusables

  • FREQ-RARE #73,079
  • LEN-LONG 8 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-DENSE 5,599
  • PHOTO-FINISH codices

Nearest frequency peer: codices (-1 rank slots)

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.

Long-tail ranks near “cofactor”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

What this shows Long-tail view: where “cofactor” sits against similarly uncommon English ranks.

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for cofactor
PropertyValue
Headwordcofactor
LanguageEnglish
Part of speechNoun
Letters8
Frequency rank#73,079
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “cofactor” in English

Word frequency stretches from the small set of words we reach for constantly (left) out to the long tail barely used once in a while (right).cofactorfalls in this rarity band:

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

Ticks step logarithmically, so each one marks a roughly tenfold drop in how often the word turns up. Rare peers in the same band: “codices” (#73,078), “Collings” (#73,080), “clusterfuck” (#73,077). Among 5,599 “C” headwords, “cofactor” is #73,079. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

cofactor is uncommon English at frequency #73,079 among 5,599 “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.

Recorded use

Wiktionary example

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

  1. Although many believe HTLV-III plays a primary role in the development of AIDS, it is still unresolved how the virus works and what cofactors, if any, play a role.

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.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "cofactor", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 8 letters (nearest by frequency rank).

Collings#73,080Clementi#73,075claptrap#73,072clanking#73,071

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

Source: FrequencyWords open word-frequency list