fast

/fɑːst/

//fɑːst// adj

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

"fast" is a 4-letter English headword indexed on PlainSpell.

The verdict

“fast” is in the everyday core of English, ranked #767 in English word frequency and used as an adjective.

#767
frequency rank, English
4
letters
5
tracked misspellings
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Firmly or securely fixed in place; stable.

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

fast vs FS
0% similar
fast vs fit
50% similar
fast vs fat
75% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for fast
PropertyValue
Headwordfast
LanguageEnglish
Part of speechAdjective
IPA/fɑːst/
Letters4
Frequency rank#767
Misspellings tracked5
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “fast” 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). fast lands here:

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

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

Spelling & Dictionary Insight

The English entry for fast is 4 letters long, classified as an adjective, and transcribed in the International Phonetic Alphabet as /fɑːst/. Corpus data places it at rank #767 in overall English word frequency, putting it firmly in the everyday core of the language. Wiktionary records 15 distinct senses for this headword, so context determines which meaning a reader should apply.

Our generated misspelling index lists 5 likely wrong-spelling variants for fast, with forms such as "afst", "fasst", and "fastt". Each variant is a distinct typo pattern an edit-distance generator flags, typically a doubled-consonant error, a silent-letter drop, or a vowel substitution. It also participates in 20 confusable-pair relationships, "FS", "fit", "fat", and more, since the words sound or look close enough that writers reach for the wrong one mid-sentence.

Etymologically, the entry records: From Middle English fast, fest, from Old English fæst (“firm, secure”), from Proto-West Germanic *fast, from Proto-Germanic *fastuz; see it for cognates and further etymology. The development of “rapid” from an original sense of “secure” apparently happened… The correct English form is fast, spelled F-A-S-T.

Definition

  1. 1
    Firmly or securely fixed in place; stable.
  2. 2
    Firm against attack; fortified by nature or art; impregnable; strong.
  3. 3
    Steadfast, with unwavering feeling. (Now mostly in set phrases like fast friend(s).)
  4. 4
    Moving with great speed, or capable of doing so; swift, rapid; light.
  5. 5
    Moving with great speed, or capable of doing so; swift, rapid; light.
  6. 6
    Of a place, characterised by business, hustle and bustle, etc.
  7. 7
    Causing unusual rapidity of play or action.
  8. 8
    Able to transfer data in a short period of time.
  9. 9
    Deep or sound (of sleep); fast asleep (of people).
  10. 10
    Not running or fading when subjected to detrimental conditions such as wetness or intense light; permanent.
  11. 11
    Tenacious; retentive.
  12. 12
    Having an extravagant lifestyle or immoral habits.
  13. 13
    Uncharacteristically mature or promiscuous for one's age.
  14. 14
    Ahead of the correct time or schedule.
  15. 15
    More sensitive to light than average.

Etymology

From Middle English fast, fest, from Old English fæst (“firm, secure”), from Proto-West Germanic *fast, from Proto-Germanic *fastuz; see it for cognates and further etymology. The development of “rapid” from an original sense of “secure” apparently happened first in the adverb and then transferred to the adjective; compare hard in expressions like “to run hard”. The original sense of “secure, firm” is now slightly archaic, but retained in the related fasten (“make secure”). Also compare close meaning change from Latin rapiō (“to snatch”) to Latin rapidus (“rapid, quick”), from Irish sciob (“to snatch”) to Irish sciobtha (“quick”).

Synonyms

quickrapidspeedyswiftspeedyeasysluttypromiscuoustight

Antonyms

slow

This word in other languages

rápido(Español)ferme(Français)fest(Deutsch)seguro(Português)

Common misspellings

Also misspelled as: afst,fasst,fastt,ffast,fsat

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of fast - expressed in single-character edits (insert, delete, or swap one letter). Bigger bars stand out at a glance; a one-edit slip is the hardest to catch.

afst2fasst1fastt1ffast1fsat2
Edit distance from "fast"

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 "fast"?
"fast" is spelled F-A-S-T. The IPA pronunciation is /fɑːst/.
What does "fast" mean?
As an adjective, "fast" means: Firmly or securely fixed in place; stable.
What words are commonly confused with "fast"?
"fast" is commonly confused with "FS", "fit", "fat". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "fast"?
The IPA (International Phonetic Alphabet) transcription for "fast" is /fɑːst/. 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 "fast"?
From Middle English fast, fest, from Old English fæst (“firm, secure”), from Proto-West Germanic *fast, from Proto-Germanic *fastuz; see it for cognates and further etymology. The development of “rapid” from an original sense of “secure” apparentl... 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 “fast”

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

  • The one correct English spelling is F-A-S-T - every other letter order is a misspelling in standard orthography.
  • Say it as /fɑːst/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
  • Don't mix it up with “FS” - see the side-by-side comparison. fast vs FS
  • Browse more English words and confusable pairs in the same reference. English words
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