ui vs und, What's the Difference?

Which to use

“ui” is an intj and “und” is a conjunction - they look or sound alike but fill different roles in a sentence.

#19,875
“ui” frequency rank: #29,551
“und” frequency rank: 49426
confusion score

Side-by-Side Comparison

Feature	ui	und
Definition	exprime surpresa, admiração, repugnância	(conjunção coordenativa) e.

Where the eye mixes ui and und

Muted = shared; highlighted = the visual trap. They share 1 letter in sequence.

2 ch

3 ch

und

Why the eye confuses ui with und

These two trip readers on the page rather than in the ear: ui is /ˈuj/ while und is /ʊnt/. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 letter(s) in length, and the parts of speech differ too (intj vs conjunction), which is usually the fastest check. Our composite confusion score for this pair is 49426, derived from the frequency rank of both members and their visual similarity.

ui is recorded at frequency rank #19,875, classified as anintj, pronounced /ˈuj/. und is at rank #29,551, tagged as aconj, pronounced /ʊnt/.

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 49426, this pair ranks #15,575 of 75,631 scored Portuguese confusable pairs - among the most confusable pairs.

Orthographic DNA of ui vs und

Shared letters: u. Private to "ui": i. Private to "und": dn.

"ui" · 2 letters · shape VV · "und" · 3 letters · shape VCC

Frequently Asked Questions

Is swapping "ui" for "und" ever safe?

No - they are not even the same part of speech. "ui" is an intj and "und" a conjunction, so a sentence built for one is usually ungrammatical with the other.

In ordinary Portuguese text, does "ui" or "und" show up more?

"ui" is the more common of the two: it sits at frequency rank #19,875 in our Portuguese list, against #29,551 for "und". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

Useful next steps

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

Full dictionary entry for "ui" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "und" - compare definitions side by side with the headword page. Word entry
This pair ranks #15,575 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"ui" and "und" also get mixed up with nearby pairs, the highest-scored neighbour is "ú vs und". Nearby pair

Confusion rank #15,575 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.