fermion

/ˈfɜːmɪɒn/

//ˈfɜːmɪɒn// noun

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

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

The verdict

“fermion” is uncommon English (frequency #89,356 among 2,507 “F” headwords), classed as a noun. The kind of spelling people second-guess.

#89,356
frequency rank, English
2,507
“F” headwords

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - Any elementary or composite particle that has half-integer spin and thus obeys Fermi–Dirac statistics and the Pauli exclusion principle (equivalently, a particle for which the wavefunction of any s...

Corpus desk

Index EN-fermion · fermion · English

fermion · rank #89,356 · 0 variants · 0 confusables

  • FREQ-RARE #89,356
  • LEN-LONG 7 letters
  • VOW-3 3 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-MID 2,507
  • PHOTO-FINISH Fera

Nearest frequency peer: Fera (-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 “fermion”

Sparse band: bars invert rank so rarer forms read shorter

corpus weight

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

Source FrequencyWords open word-frequency list As of September 3, 2026
Key facts for fermion
PropertyValue
Headwordfermion
LanguageEnglish
Part of speechNoun
IPA/ˈfɜːmɪɒn/
Letters7
Frequency rank#89,356
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “fermion” 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).fermionfalls in this rarity band:

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

Scale is logarithmic (each tick is 10× rarer). Rare peers in the same band: “Fera” (#89,355), “feis” (#89,353), “feigns” (#89,352). Among 2,507 “F” headwords, “fermion” is #89,356. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

fermion is uncommon English at frequency #89,356 among 2,507 “F” headwords, classed as anoun, transcribed /ˈfɜːmɪɒn/. Rarity is why readers land here mid-draft. 2 senses are on record.

Zero misspellings are on record for fermion in our index, typically a sign the spelling maps closely to how the word sounds. This headword has no recorded confusable partner, suggesting its spelling stands apart enough that readers rarely confuse it with something else.

Etymologically, the entry records: From Fermi + -on. Named after Italian-American physicist Enrico Fermi. Coined by English physicist Paul Dirac in 1945 in a lecture titled "Developments in Atomic Theory". The correct English form is fermion, spelled F-E-R-M-I-O-N.

Definition

  1. 1
    Any elementary or composite particle that has half-integer spin and thus obeys Fermi–Dirac statistics and the Pauli exclusion principle (equivalently, a particle for which the wavefunction of any system of identical such particles changes sign whenever two are swapped); a baryon, a lepton or a quark;
  2. 2
    Any elementary or composite particle that has half-integer spin and thus obeys Fermi–Dirac statistics and the Pauli exclusion principle (equivalently, a particle for which the wavefunction of any system of identical such particles changes sign whenever two are swapped); a baryon, a lepton or a quark; (slightly more loosely) any such particle or any composite particle composed of fermions.

Recorded use

Wiktionary examples

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

  1. The fermions treated by the Standard Model are the (composite) baryons and the (elementary) leptons and quarks.
  2. According to the spin–statistics theorem, the wavefunction of a system of identical fermions (particles of half-integer spin) is antisymmetric under the operation of swapping any two particles.

Etymology

From Fermi + -on. Named after Italian-American physicist Enrico Fermi. Coined by English physicist Paul Dirac in 1945 in a lecture titled "Developments in Atomic Theory".

Synonyms

fermion

This word in other languages

fermión(Español)fermion(Français)Fermion(Deutsch)

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 "fermion"?
"fermion" is spelled F-E-R-M-I-O-N. The IPA pronunciation is /ˈfɜːmɪɒn/.
What does "fermion" mean?
As a noun, "fermion" means: Any elementary or composite particle that has half-integer spin and thus obeys Fermi–Dirac statistics and the Pauli exclusion principle (equivalently, a particle for which the wavefunction of any s...
How do you pronounce "fermion"?
The IPA (International Phonetic Alphabet) transcription for "fermion" is /ˈfɜːmɪɒn/. 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 "fermion"?
From Fermi + -on. Named after Italian-American physicist Enrico Fermi. Coined by English physicist Paul Dirac in 1945 in a lecture titled "Developments in Atomic Theory". 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 "fermion", not the corpus desk frequency band.

Same letter count

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

Fedorov#89,349Flossie#89,367flytrap#89,370Evelyne#89,339

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

Source: FrequencyWords open word-frequency list