Which to use
“what” is a determiner and “when” is an adverb - they look or sound alike but fill different roles in a sentence.
- #46
- “what” frequency rank
- #48
- “when” frequency rank
- 94
- confusion score
Side-by-Side Comparison
| Feature | what | when |
|---|---|---|
| Definition | Which, especially which of an open-ended set of possibilities. | At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time. |
Where the eye mixes what and when
Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.
Visual trap between what and when
These two trip readers on the page rather than in the ear: what is /wɒt/ while when is /ˈwɛn/. 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 (determiner vs adverb), which is usually the fastest check. Our composite confusion score for this pair is 94, derived from the frequency rank of both members and their visual similarity.
what is recorded at frequency rank #46, classified as adet, pronounced /wɒt/. when is at rank #48, tagged as anadv, pronounced /ˈwɛn/.
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 94, this pair ranks #529,895 of 530,003 scored English confusable pairs - a relatively easy-to-tell-apart pair.
Orthographic DNA of what vs when
Shared letters: hw. Private to "what": at. Private to "when": en.
"what" · 4 letters · shape CCVC · "when" · 4 letters · shape CCVC
Known mistypes of this pair
Frequently Asked Questions
Can "what" and "when" be used interchangeably?
Which is more common, "what" or "when"?
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 "what" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "when" - compare definitions side by side with the headword page. Word entry
- This pair ranks #529,895 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "what" and "when" also get mixed up with nearby pairs, the highest-scored neighbour is "Whalen vs when". Nearby pair
- Recorded mistypes exist for at least one side of this pair, useful when a spell-checker or OCR lands on the wrong form. See mistypes
Confusion rank #529,895 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.