functor

/ˈfʌŋktə/

//ˈfʌŋktə// noun

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

"functor" is a 7-letter English headword indexed on PlainSpell.

The verdict

“functor” is uncommon English (frequency #79,529 among 2,507 “F” headwords), classed as a noun. The kind of spelling people second-guess.

#79,529
frequency rank, English
2,507
“F” headwords

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

Corpus desk

Index EN-functor · functor · English

functor · rank #79,529 · 0 variants · 0 confusables

  • FREQ-RARE #79,529
  • LEN-LONG 7 letters
  • VOW-2 2 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-MID 2,507
  • PHOTO-FINISH fulsome

Nearest frequency peer: fulsome (-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 “functor”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

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

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for functor
PropertyValue
Headwordfunctor
LanguageEnglish
Part of speechNoun
IPA/ˈfʌŋktə/
Letters7
Frequency rank#79,529
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “functor” in English

This scale runs from the tiny cluster of words that carry ordinary speech (left) to the long tail of words almost nobody reaches for (right).functorfalls in this rarity band:

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

The axis is logarithmic, with each marked tick roughly ten times rarer than the last. Rare peers in the same band: “fulsome” (#79,528), “fusilier” (#79,530), “Fujimoto” (#79,527). Among 2,507 “F” headwords, “functor” is #79,529. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

functor is uncommon English at frequency #79,529 among 2,507 “F” headwords, classed as anoun, transcribed /ˈfʌŋktə/. Rarity is why readers land here mid-draft. 4 senses are on record.

Zero misspellings are on record for functor in our index, and the word's spelling is regular enough that our generator found nothing worth flagging. No confusable counterpart is on file for this word, since no other headword is close enough in sound or shape to pair with it.

Etymologically, the entry records: From function, modeled after factor. The correct English form is functor, spelled F-U-N-C-T-O-R.

Definition

  1. 1
    A function word.
  2. 2
    A function object.
  3. 3
    A category homomorphism; a morphism from a source category to a target category which maps objects to objects and arrows to arrows (either covariantly or contravariantly), in such a way as to preserve morphism composition and identities.
  4. 4
    A structure allowing a function to apply within a generic type, in a way that is conceptually similar to a functor in category theory.

Recorded use

Wiktionary examples

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

  1. In the category of categories #92;mathbf#123;Cat#125; the objects are categories and the morphisms are functors.
  2. 1991, Natalie Wadhwa (translator), Yu. A. Brudnyǐ, N. Ya. Krugljak, Interpolation Functors and Interpolation Spaces, Volume I, Elsevier (North-Holland), page 143, Choosing for U the operation of closure, regularization or relative completion, we obtain from a given functor ℱ∈𝒥ℱ the functors ◌̅F: overrightarrow X→◌̅F( overrightarrow X),F⁰: overrightarrow…

Etymology

From function, modeled after factor.

This word in other languages

foncteur(Français)

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 "functor"?
"functor" is spelled F-U-N-C-T-O-R. The IPA pronunciation is /ˈfʌŋktə/.
What does "functor" mean?
As a noun, "functor" means: A function word.
How do you pronounce "functor"?
The IPA (International Phonetic Alphabet) transcription for "functor" is /ˈfʌŋktə/. 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 "functor"?
From function, modeled after 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 "functor", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 7 letters (nearest by frequency rank).

fulsome#79,528fuckwit#79,526gauchos#79,538flanged#79,514

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

Source: FrequencyWords open word-frequency list