RSFvsrustWhich spelling fits?

Which to use

“RSF” and “rust” are a confusable French pair: similar on the page, but distinct in meaning, check the gloss before you choose.

#44,703
“RSF” frequency rank
#37,050
“rust” frequency rank
81753
confusion score

Side-by-Side Comparison

Feature RSF rust
Definition Abréviation de réacteur à sels fondus. Rouille.

Where the eye mixes RSF and rust

Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.

3 ch
RSF
4 ch
rust

Visual trap between RSF and rust

A purely visual mix-up. RSF (\ɛ.ʁɛ.sɛf\) and rust (\ɻʌst\) are said differently, so reading them aloud is the quickest way to catch the wrong one. On the page they stay close: they differ by 1 letter(s) in length. Our composite confusion score for this pair is 81753, derived from the frequency rank of both members and their visual similarity.

RSF is recorded at frequency rank #44,703, classified as anoun, pronounced \ɛ.ʁɛ.sɛf\. rust is at rank #37,050, tagged as anoun, pronounced \ɻʌst\.

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 81753, this pair ranks #18,092 of 440,172 scored French confusable pairs - among the most confusable pairs.

Orthographic DNA of RSF vs rust

Shared letters: rs. Private to "RSF": f. Private to "rust": tu.

"RSF" · 3 letters · shape CCC  ·  "rust" · 4 letters · shape CVCC

Known mistypes of this pair

  • rustrrust · rsut · russt · rustt · ruts · urst

Frequently Asked Questions

Do "RSF" and "rust" mean the same thing in a sentence?
No. They are said differently (\ɛ.ʁɛ.sɛf\ versus \ɻʌst\) and carry different meanings; reading the sentence aloud is usually enough to catch the wrong one.
In ordinary French text, does "RSF" or "rust" show up more?
"rust" is the more common of the two: it sits at frequency rank #37,050 in our French list, against #44,703 for "RSF". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

After this comparison

Pronunciation already separates them, if the page still looks alike, the dictionary links below settle it.

  • Full dictionary entry for "RSF" with definition, IPA, and generated misspellings. Word entry
  • Full dictionary entry for "rust" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #18,092 of 440,172 scored French confusable pairs in this corpus vintage. Corpus statistics
  • "RSF" and "rust" also get mixed up with nearby pairs, the highest-scored neighbour is "rog vs RSF". 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 #18,092 of 440,172 scored French pairs, corpus vintage 2026-09-03, not spelling advice.

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

Source: FrequencyWords open word-frequency list