sei vs spy, What's the Difference?

Which to use

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

#48,072
“sei” frequency rank: #48,092
“spy” frequency rank: 96164
confusion score

Side-by-Side Comparison

Feature	sei	spy
Definition	Seis.	Espía.

Where the eye mixes sei and spy

Muted = shared; highlighted = the visual trap. They share 1 letter in sequence. sei (CVV) and spy (CCV) run the same length but a different consonant-vowel pattern - the shape difference is usually the fastest tell.

3 ch

sei

3 ch

spy

Why the eye confuses sei with spy

These two trip readers on the page rather than in the ear: sei is /s̺ej/ while spy is /spaɪ/. Spoken aloud the problem disappears. In writing it persists, because they share most of their letters but differ in 2 positions, and the parts of speech differ too (num vs noun), which is usually the fastest check. Our composite confusion score for this pair is 96164, derived from the frequency rank of both members and their visual similarity.

sei is recorded at frequency rank #48,072, classified as anum, pronounced /s̺ej/. spy is at rank #48,092, tagged as anoun, pronounced /spaɪ/.

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 96164, this pair ranks #385 of 323,831 scored Spanish confusable pairs - among the most confusable pairs.

Orthographic DNA of sei vs spy

Shared letters: s. Private to "sei": ei. Private to "spy": py.

"sei" · 3 letters · shape CVV · "spy" · 3 letters · shape CCV

Frequently Asked Questions

Is swapping "sei" for "spy" ever safe?

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

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

"sei" is the more common of the two: it sits at frequency rank #48,072 in our Spanish list, against #48,092 for "spy". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

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 "sei" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "spy" - compare definitions side by side with the headword page. Word entry
This pair ranks #385 of 323,831 scored Spanish confusable pairs in this corpus vintage. Corpus statistics
"sei" and "spy" also get mixed up with nearby pairs, the highest-scored neighbour is "sei vs stem". Nearby pair

Confusion rank #385 of 323,831 scored Spanish pairs, corpus vintage 2026-09-03, not spelling advice.