si vs sky, What's the Difference?

Which to use

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

#482
“si” frequency rank: #7,084
“sky” frequency rank: 7566
confusion score

Side-by-Side Comparison

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

Where the eye mixes si and sky

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

2 ch

3 ch

sky

Look-alike desk: si vs sky

These two trip readers on the page rather than in the ear: si is /ˈsi/ while sky is /skaɪ/. 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 (pronoun vs noun), which is usually the fastest check. Our composite confusion score for this pair is 7566, derived from the frequency rank of both members and their visual similarity.

si is recorded at frequency rank #482, classified as apron, pronounced /ˈsi/. sky is at rank #7,084, tagged as anoun, pronounced /skaɪ/.

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 7566, this pair ranks #66,548 of 75,631 scored Portuguese confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of si vs sky

Shared letters: s. Private to "si": i. Private to "sky": ky.

"si" · 2 letters · shape CV · "sky" · 3 letters · shape CCV

Frequently Asked Questions

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

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

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

"si" is the more common of the two: it sits at frequency rank #482 in our Portuguese list, against #7,084 for "sky". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

After this comparison

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

Full dictionary entry for "si" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "sky" - compare definitions side by side with the headword page. Word entry
This pair ranks #66,548 of 75,631 scored Portuguese confusable pairs in this corpus vintage. Corpus statistics
"si" and "sky" also get mixed up with nearby pairs, the highest-scored neighbour is "Sau vs sky". Nearby pair

Confusion rank #66,548 of 75,631 scored Portuguese pairs, corpus vintage 2026-09-03, not spelling advice.