Which to use
“FIS” and “FOSS” are a confusable English pair: similar on the page, but distinct in meaning, check the gloss before you choose.
- #40,245
- “FIS” frequency rank
- #33,655
- “FOSS” frequency rank
- 73900
- confusion score
Side-by-Side Comparison
| Feature | FIS | FOSS |
|---|---|---|
| Definition | Initialism of flight information service. | Initialism of Free and Open Source Software. |
Letter map: FIS vs FOSS
Shared letters muted; letters that set FIS and FOSS apart highlighted. Shared run: 2. FIS runs 3 letters (CVC) against FOSS's 4 (CVCC) - the length gap alone is often enough to separate them once you know to check it.
Pair insight - FIS / FOSS
FIS and FOSS are indexed as a confusable English pair. We have no recorded pronunciation or part of speech for both members, so the spelling overlap is what we can show you: they differ by 1 letter(s) in length. Our composite confusion score for this pair is 73900, derived from the frequency rank of both members and their visual similarity.
FIS is recorded at frequency rank #40,245, classified as anoun. FOSS is at rank #33,655, tagged as anoun, pronounced /fɒs/.
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 73900, this pair ranks #38,051 of 530,003 scored English confusable pairs - among the most confusable pairs.
Orthographic DNA of FIS vs FOSS
Shared letters: fs. Private to "FIS": i. Private to "FOSS": o.
"FIS" · 3 letters · shape CVC · "FOSS" · 4 letters · shape CVCC
Known mistypes of this pair
- FOSS ← ffoss · fos · fsos · ofss
Frequently Asked Questions
Is swapping "FIS" for "FOSS" ever safe?
In ordinary English text, does "FIS" or "FOSS" show up more?
After this comparison
Pair "FIS" vs "FOSS" is on the table, pick a follow-up below.
- Full dictionary entry for "FIS" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "FOSS" - compare definitions side by side with the headword page. Word entry
- This pair ranks #38,051 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "FIS" and "FOSS" also get mixed up with nearby pairs, the highest-scored neighbour is "FIS vs foh". 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 #38,051 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.