s vs si, What's the Difference?

Which to use

“s” is a symbol and “si” is a pronoun - they look or sound alike but fill different roles in a sentence.

#511
“s” frequency rank: #482
“si” frequency rank: 993
confusion score

Side-by-Side Comparison

Feature	s	si
Definition	símbolo de segundo	refere-se à terceira pessoa, indica reflexividade e é usado após preposição (a, de, em, contra, sobre, por, etc., exceto com)

Letter map: s vs si

Shared letters muted; letters that set s and si apart highlighted. Shared run: 1.

1 ch

2 ch

Role in the sentence - s and si

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: s is asymbol and siapronoun. On the page they differ by 1 extra letter(s) - “s” sits inside “si”. Our composite confusion score for this pair is 993, derived from the frequency rank of both members and their visual similarity.

s is recorded at frequency rank #511, classified as asymbol. si is at rank #482, tagged as apron, pronounced /ˈsi/.

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 993, this pair ranks #74,637 of 75,631 scored Portuguese confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of s vs si

Shared letters: s. Private to "s": -. Private to "si": i.

"s" · 1 letters · shape C · "si" · 2 letters · shape CV

Frequently Asked Questions

Can "s" and "si" be used interchangeably?

No - they are not even the same part of speech. "s" is a symbol and "si" a pronoun, so a sentence built for one is usually ungrammatical with the other.

Frequency check: "s" vs "si" - which ranks higher?

"si" is the more common of the two: it sits at frequency rank #482 in our Portuguese list, against #511 for "s". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

What to do next

You've compared "s" and "si". Here's where to go from here.

Full dictionary entry for "s" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "si" - compare definitions side by side with the headword page. Word entry
This pair ranks #74,637 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"s" and "si" also get mixed up with nearby pairs, the highest-scored neighbour is "s vs Sau". Nearby pair

Confusion rank #74,637 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.