Which to use
“sec” is an adjective and “sei” is a num - they look or sound alike but fill different roles in a sentence.
- #17,813
- “sec” frequency rank
- #48,072
- “sei” frequency rank
- 65885
- confusion score
Side-by-Side Comparison
| Feature | sec | sei |
|---|---|---|
| Definition | Seco | Seis. |
Where the eye mixes sec and sei
Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.
Visual trap between sec and sei
These two trip readers on the page rather than in the ear: sec is [sɛk] while sei is /s̺ej/. Spoken aloud the problem disappears. In writing it persists, because they differ by a single letter - c in “sec” becomes i in “sei”, and the parts of speech differ too (adjective vs num), which is usually the fastest check. Our composite confusion score for this pair is 65885, derived from the frequency rank of both members and their visual similarity.
sec is recorded at frequency rank #17,813, classified as anadj, pronounced [sɛk]. 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 65885, this pair ranks #41,358 of 323,831 scored Spanish confusable pairs - among the most confusable pairs.
Orthographic DNA of sec vs sei
Shared letters: es. Private to "sec": c. Private to "sei": i.
"sec" · 3 letters · shape CVC · "sei" · 3 letters · shape CVV
Frequently Asked Questions
Can "sec" and "sei" be used interchangeably?
Which is more common, "sec" or "sei"?
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 "sec" 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 #41,358 of 323,831 scored Spanish confusable pairs in this corpus vintage. Corpus statistics
- "sec" and "sei" also get mixed up with nearby pairs, the highest-scored neighbour is "sei vs stem". Nearby pair
Confusion rank #41,358 of 323,831 scored Spanish pairs, corpus vintage 2026-09-03, not spelling advice.