sei vs série, What's the Difference?

Which to use

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

#118
“sei” frequency rank: #337
“série” frequency rank: 455
confusion score

Side-by-Side Comparison

Feature	sei	série
Definition	expressa que aquilo ouvido que foi dito ou afirmado por alguém não é tomado como sendo a verdade	conjunto de pessoas ou itens com ordenação sequencial:

Letter map: sei vs série

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

3 ch

sei

5 ch

série

Grammar separator: sei vs série

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: sei is anintj and sérieanoun. On the page they differ by 2 letter(s) in length. Our composite confusion score for this pair is 455, derived from the frequency rank of both members and their visual similarity.

sei is recorded at frequency rank #118, classified as anintj. série is at rank #337, tagged as anoun, pronounced /ˈsɛ.ɾi/.

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 455, this pair ranks #75,202 of 75,631 scored Portuguese confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of sei vs série

Shared letters: eis. Private to "sei": -. Private to "série": ré.

"sei" · 3 letters · shape CVV · "série" · 5 letters · shape CVCVV

Frequently Asked Questions

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

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

Frequency check: "sei" vs "série" - which ranks higher?

"sei" is the more common of the two: it sits at frequency rank #118 in our Portuguese list, against #337 for "série". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

After this comparison

Pair "sei" vs "série" is on the table, pick a follow-up below.

Full dictionary entry for "sei" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "série" - compare definitions side by side with the headword page. Word entry
This pair ranks #75,202 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"sei" and "série" also get mixed up with nearby pairs, the highest-scored neighbour is "Sau vs sei". Nearby pair

Confusion rank #75,202 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.