Which to use
“au” is an article and “auf” is a preposition - they look or sound alike but fill different roles in a sentence.
- #24
- “au” frequency rank
- #25,894
- “auf” frequency rank
- 25918
- confusion score
Side-by-Side Comparison
| Feature | au | auf |
|---|---|---|
| Definition | Contraction de la préposition à et de l'article défini le. | Sur, avec notion d'immobilité. |
Where the eye mixes au and auf
Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.
Why the eye confuses au with auf
These two trip readers on the page rather than in the ear: au is \o\ while auf is \aʊ̯f\. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 extra letter(s) - “au” sits inside “auf”, and the parts of speech differ too (article vs preposition), which is usually the fastest check. Our composite confusion score for this pair is 25918, derived from the frequency rank of both members and their visual similarity.
au is recorded at frequency rank #24, classified as anarticle, pronounced \o\. auf is at rank #25,894, tagged as aprep, pronounced \aʊ̯f\.
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 25918, this pair ranks #338,134 of 440,172 scored French confusable pairs - a relatively easy-to-tell-apart pair.
Orthographic DNA of au vs auf
Shared letters: au. Private to "au": -. Private to "auf": f.
"au" · 2 letters · shape VV · "auf" · 3 letters · shape VVC
Frequently Asked Questions
Can "au" and "auf" be used interchangeably?
In ordinary French text, does "au" or "auf" show up more?
What to do next
Pronunciation already separates them, if the page still looks alike, the dictionary links below settle it.
- Full dictionary entry for "au" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "auf" - compare definitions side by side with the headword page. Word entry
- This pair ranks #338,134 of 440,172 scored French confusable pairs in this corpus vintage. Corpus statistics
- "au" and "auf" also get mixed up with nearby pairs, the highest-scored neighbour is "auf vs aur". Nearby pair
Confusion rank #338,134 of 440,172 scored French pairs, corpus vintage 2026-09-03, not spelling advice.