Which to use
“fast” is an adjective and “fis” is a verb - they look or sound alike but fill different roles in a sentence.
- #16,583
- “fast” frequency rank
- #37,094
- “fis” frequency rank
- 53677
- confusion score
Side-by-Side Comparison
| Feature | fast | fis |
|---|---|---|
| Definition | Rápido, veloz. | Primera persona del singular (je) del pretérito perfecto simple de indicativo de faire. |
Where the eye mixes fast and fis
Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.
Why the eye confuses fast with fis
These two trip readers on the page rather than in the ear: fast is /fɑːst/ while fis is [fi]. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 letter(s) in length, and the parts of speech differ too (adjective vs verb), which is usually the fastest check. Our composite confusion score for this pair is 53677, derived from the frequency rank of both members and their visual similarity.
fast is recorded at frequency rank #16,583, classified as anadj, pronounced /fɑːst/. fis is at rank #37,094, tagged as averb, pronounced [fi].
Glosses for this pair are partially populated in our dataset, but the full side-by-side definitions above should still guide you to the right choice.
With a confusion score of 53677, this pair ranks #86,756 of 323,831 scored Spanish confusable pairs - roughly mid-pack for confusability.
Orthographic DNA of fast vs fis
Shared letters: fs. Private to "fast": at. Private to "fis": i.
"fast" · 4 letters · shape CVCC · "fis" · 3 letters · shape CVC
Known mistypes of this pair
- fast ← afst · fasst · fastt · fats · ffast · fsat
Frequently Asked Questions
Do "fast" and "fis" mean the same thing in a sentence?
Frequency check: "fast" vs "fis" - which ranks higher?
Useful next steps
Pronunciation already separates them, if the page still looks alike, the dictionary links below settle it.
- Full dictionary entry for "fast" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "fis" - compare definitions side by side with the headword page. Word entry
- This pair ranks #86,756 of 323,831 scored Spanish confusable pairs in this corpus vintage. Corpus statistics
- "fast" and "fis" also get mixed up with nearby pairs, the highest-scored neighbour is "filos vs fis". Nearby pair
- Recorded mistypes exist for at least one side of this pair, useful when a spell-checker or OCR lands on the wrong form. See mistypes
Confusion rank #86,756 of 323,831 scored Spanish pairs, corpus vintage 2026-09-03, not spelling advice.