sec vs si, What's the Difference?

Which to use

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

#19,268
“sec” frequency rank: #482
“si” frequency rank: 19750
confusion score

Side-by-Side Comparison

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

Where the eye mixes sec and si

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

3 ch

sec

2 ch

Visual trap between sec and si

These two trip readers on the page rather than in the ear: sec is \sɛk\ while si is /ˈsi/. 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 (adjective vs pronoun), which is usually the fastest check. Our composite confusion score for this pair is 19750, 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\. 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 19750, this pair ranks #50,908 of 75,631 scored Portuguese confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of sec vs si

Shared letters: s. Private to "sec": ce. Private to "si": i.

"sec" · 3 letters · shape CVC · "si" · 2 letters · shape CV

Frequently Asked Questions

Do "sec" and "si" mean the same thing in a sentence?

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

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

"si" is the more common of the two: it sits at frequency rank #482 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.

What to do next

Visual near-miss handled. Browse the word pages or a neighbour when the next look-alike shows up.

Full dictionary entry for "sec" 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 #50,908 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"sec" and "si" also get mixed up with nearby pairs, the highest-scored neighbour is "Sau vs sec". Nearby pair

Confusion rank #50,908 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.