foi vs fui, What's the Difference?

Which to use

“foi” and “fui” are a confusable Portuguese pair: similar on the page, but distinct in meaning, check the gloss before you choose.

#26
“foi” frequency rank: #365
“fui” frequency rank: 391
confusion score

Side-by-Side Comparison

Feature	foi	fui
Definition	terceira pessoa do singular do pretérito perfeito do indicativo do verbo ser	primeira pessoa do singular do pretérito perfeito simples do indicativo do verbo ir:

Where the eye mixes foi and fui

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

3 ch

foi

3 ch

fui

Visual trap between foi and fui

A purely visual mix-up. foi (/ˈfoj/) and fui (/ˈfuj/) 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 a single letter - o in “foi” becomes u in “fui”. Our composite confusion score for this pair is 391, derived from the frequency rank of both members and their visual similarity.

foi is recorded at frequency rank #26, classified as averb, pronounced /ˈfoj/. fui is at rank #365, tagged as averb, pronounced /ˈfuj/.

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 391, this pair ranks #75,245 of 75,631 scored Portuguese confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of foi vs fui

Shared letters: fi. Private to "foi": o. Private to "fui": u.

"foi" · 3 letters · shape CVV · "fui" · 3 letters · shape CVV

Frequently Asked Questions

Can "foi" and "fui" be used interchangeably?

No. They are said differently (/ˈfoj/ versus /ˈfuj/) and carry different meanings; reading the sentence aloud is usually enough to catch the wrong one.

Which is more common, "foi" or "fui"?

"foi" is the more common of the two: it sits at frequency rank #26 in our Portuguese list, against #365 for "fui". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

Useful next steps

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

Full dictionary entry for "foi" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "fui" - compare definitions side by side with the headword page. Word entry
This pair ranks #75,245 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"foi" and "fui" also get mixed up with nearby pairs, the highest-scored neighbour is "faia vs fui". Nearby pair

Confusion rank #75,245 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.