sec vs sei, What's the Difference?

Which to use

“sec” is an adjective and “sei” is an intj - they look or sound alike but fill different roles in a sentence.

#19,268
“sec” frequency rank: #118
“sei” frequency rank: 19386
confusion score

Side-by-Side Comparison

Feature	sec	sei
Definition	seco	expressa que aquilo ouvido que foi dito ou afirmado por alguém não é tomado como sendo a verdade

Letter map: sec vs sei

Shared letters muted; letters that set sec and sei apart highlighted. Shared run: 2.

3 ch

sec

3 ch

sei

Part-of-speech tell for sec / sei

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: sec is anadjective and seianintj. On the page they differ by a single letter - c in “sec” becomes i in “sei”. Our composite confusion score for this pair is 19386, derived from the frequency rank of both members and their visual similarity.

sec is recorded at frequency rank #19,268, classified as anadj, pronounced \sɛk\. sei is at rank #118, tagged as anintj.

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 19386, this pair ranks #51,349 of 75,631 scored Portuguese confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of sec vs sei

Shared letters: es. Private to "sec": c. Private to "sei": i.

"sec" · 3 letters · shape CVC · "sei" · 3 letters · shape CVV

Frequently Asked Questions

Can "sec" and "sei" be used interchangeably?

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

Which is more common, "sec" or "sei"?

"sei" is the more common of the two: it sits at frequency rank #118 in our Portuguese list, against #19,268 for "sec". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

After this comparison

Done with this confusable. These links stay specific to "sec" and "sei".

Full dictionary entry for "sec" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "sei" - compare definitions side by side with the headword page. Word entry
This pair ranks #51,349 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"sec" and "sei" also get mixed up with nearby pairs, the highest-scored neighbour is "Sau vs sec". Nearby pair

Confusion rank #51,349 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.