se vs sei, What's the Difference?

Which to use

“se” is a pronoun and “sei” is a num - they look or sound alike but fill different roles in a sentence.

#11
“se” frequency rank: #48,072
“sei” frequency rank: 48083
confusion score

Side-by-Side Comparison

Feature	se	sei
Definition	(se reflexivo) Pronombre reflexivo anafórico que establece una correferencialidad con el sujeto de la oración en tercera persona. Equivalente al caso dativo, por lo que admite el refuerzo “a sí mismo”.	Seis.

Where the eye mixes se and sei

Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.

2 ch

3 ch

sei

Look-alike desk: se vs sei

These two trip readers on the page rather than in the ear: se is [se] while sei is /s̺ej/. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 extra letter(s) - “se” sits inside “sei”, and the parts of speech differ too (pronoun vs num), which is usually the fastest check. Our composite confusion score for this pair is 48083, derived from the frequency rank of both members and their visual similarity.

se is recorded at frequency rank #11, classified as apron, pronounced [se]. sei is at rank #48,072, tagged as anum, pronounced /s̺ej/.

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 48083, this pair ranks #116,434 of 323,831 scored Spanish confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of se vs sei

Shared letters: es. Private to "se": -. Private to "sei": i.

"se" · 2 letters · shape CV · "sei" · 3 letters · shape CVV

Frequently Asked Questions

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

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

In ordinary Spanish text, does "se" or "sei" show up more?

"se" is the more common of the two: it sits at frequency rank #11 in our Spanish list, against #48,072 for "sei". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

After this comparison

Pronunciation already separates them, if the page still looks alike, the dictionary links below settle it.

Full dictionary entry for "se" 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 #116,434 of 323,831 scored Spanish confusable pairs in this corpus vintage. Corpus statistics
"se" and "sei" also get mixed up with nearby pairs, the highest-scored neighbour is "sei vs stem". Nearby pair

Confusion rank #116,434 of 323,831 scored Spanish pairs, corpus vintage 2026-09-03, not spelling advice.