Which to use
“fir” and “firth” are a confusable English pair: similar on the page, but distinct in meaning, check the gloss before you choose.
- #15,408
- “fir” frequency rank
- #22,972
- “firth” frequency rank
- 38380
- confusion score
Side-by-Side Comparison
| Feature | fir | firth |
|---|---|---|
| Definition | A conifer of the genus Abies. | An arm or inlet of the sea; a river estuary. |
Where the eye mixes fir and firth
Muted = shared; highlighted = the visual trap. They share 3 letters in sequence.
Why the eye confuses fir with firth
A purely visual mix-up. fir (/fɜː/) and firth (/fɜːθ/) 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 2 extra letter(s) - “fir” sits inside “firth”. Our composite confusion score for this pair is 38380, derived from the frequency rank of both members and their visual similarity.
fir is recorded at frequency rank #15,408, classified as anoun, pronounced /fɜː/. firth is at rank #22,972, tagged as anoun, pronounced /fɜːθ/.
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 38380, this pair ranks #286,410 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.
Orthographic DNA of fir vs firth
Shared letters: fir. Private to "fir": -. Private to "firth": ht.
"fir" · 3 letters · shape CVC · "firth" · 5 letters · shape CVCCC
Known mistypes of this pair
- firth ← ffirth · firht · firrth · firthh · firtth · fitrh · ifrth
Frequently Asked Questions
Do "fir" and "firth" mean the same thing in a sentence?
Frequency check: "fir" vs "firth" - which ranks higher?
Useful next steps
Visual near-miss handled. Browse the word pages or a neighbour when the next look-alike shows up.
- Full dictionary entry for "fir" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "firth" - compare definitions side by side with the headword page. Word entry
- This pair ranks #286,410 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "fir" and "firth" also get mixed up with nearby pairs, the highest-scored neighbour is "firth vs frith". 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 #286,410 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.