Which to use
“dud” is a noun and “dup” is a verb - they look or sound alike but fill different roles in a sentence.
- #29,251
- “dud” frequency rank
- #28,177
- “dup” frequency rank
- 57428
- confusion score
Side-by-Side Comparison
| Feature | dud | dup |
|---|---|---|
| Definition | A device or machine that is useless because it does not work properly or has failed to work, such as a bomb, or explosive projectile. | to open (a door, gate etc.) |
Where the eye mixes dud and dup
Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.
Visual trap between dud and dup
These two trip readers on the page rather than in the ear: dud is /dʌd/ while dup is /dʌp/. Spoken aloud the problem disappears. In writing it persists, because they differ by a single letter - d in “dud” becomes p in “dup”, and the parts of speech differ too (noun vs verb), which is usually the fastest check. Our composite confusion score for this pair is 57428, derived from the frequency rank of both members and their visual similarity.
dud is recorded at frequency rank #29,251, classified as anoun, pronounced /dʌd/. dup is at rank #28,177, tagged as averb, pronounced /dʌp/.
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 57428, this pair ranks #119,344 of 530,003 scored English confusable pairs - among the most confusable pairs.
Orthographic DNA of dud vs dup
Shared letters: du. Private to "dud": -. Private to "dup": p.
"dud" · 3 letters · shape CVC · "dup" · 3 letters · shape CVC
Frequently Asked Questions
Is swapping "dud" for "dup" ever safe?
Which is more common, "dud" or "dup"?
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 "dud" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "dup" - compare definitions side by side with the headword page. Word entry
- This pair ranks #119,344 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "dud" and "dup" also get mixed up with nearby pairs, the highest-scored neighbour is "dox vs dud". Nearby pair
Confusion rank #119,344 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.