Which to use
“FOSS” and “fossa” are a confusable English pair: similar on the page, but distinct in meaning, check the gloss before you choose.
- #33,655
- “FOSS” frequency rank
- #48,755
- “fossa” frequency rank
- 82410
- confusion score
Side-by-Side Comparison
| Feature | FOSS | fossa |
|---|---|---|
| Definition | Initialism of Free and Open Source Software. | A pit, groove, cavity, or depression. |
Where the eye mixes FOSS and fossa
Muted = shared; highlighted = the visual trap. They share 4 letters in sequence. FOSS runs 4 letters (CVCC) against fossa's 5 (CVCCV) - the length gap alone is often enough to separate them once you know to check it.
Visual trap between FOSS and fossa
A purely visual mix-up. FOSS (/fɒs/) and fossa (/ˈfɒsə/) 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 extra letter(s) - “FOSS” sits inside “fossa”. Our composite confusion score for this pair is 82410, derived from the frequency rank of both members and their visual similarity.
FOSS is recorded at frequency rank #33,655, classified as anoun, pronounced /fɒs/. fossa is at rank #48,755, tagged as anoun, pronounced /ˈfɒsə/.
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 82410, this pair ranks #15,772 of 530,003 scored English confusable pairs - among the most confusable pairs.
Orthographic DNA of FOSS vs fossa
Shared letters: fos. Private to "FOSS": -. Private to "fossa": a.
"FOSS" · 4 letters · shape CVCC · "fossa" · 5 letters · shape CVCCV
Known mistypes of this pair
Frequently Asked Questions
Is swapping "FOSS" for "fossa" ever safe?
Which is more common, "FOSS" or "fossa"?
After this comparison
Pronunciation already separates them, if the page still looks alike, the dictionary links below settle it.
- Full dictionary entry for "FOSS" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "fossa" - compare definitions side by side with the headword page. Word entry
- This pair ranks #15,772 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "FOSS" and "fossa" also get mixed up with nearby pairs, the highest-scored neighbour is "fess vs fossa". 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 #15,772 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.