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 spellings diverge
Shared letters are muted; the letters that actually set what and when apart are highlighted. They share 2 letters in sequence, which is exactly why the eye skips the difference.
Spelling & Dictionary Insight
what and when form a confusable pair in the English index, two distinct headwords that are easily confused because they look alike, sound alike, or both. They share most of their letters but differ in 2 positions - close enough that the eye skips over the difference, far enough that meaning fully diverges. 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.
Frequency comparison
Frequently Asked Questions
Can "what" and "when" be used interchangeably?
Remembering what vs when
The fastest way to pick the right one every time.
- Check the role first: if you need a determiner, it's “what”; for an adverb, it's “when”.
- See each word in full, definition, IPA, etymology and its other confusables. Full “what” entry
- Browse more pairs most likely to be confused. Most confusable