Which to use
“under” is a preposition and “undo” is a verb - they look or sound alike but fill different roles in a sentence.
- #180
- “under” frequency rank
- #13,631
- “undo” frequency rank
- 13811
- confusion score
Side-by-Side Comparison
| Feature | under | undo |
|---|---|---|
| Definition | Beneath; below; at or to the bottom of, or the area covered or surmounted by. | To reverse the effects of an action. |
Where the eye mixes under and undo
Muted = shared; highlighted = the visual trap. They share 3 letters in sequence.
Look-alike desk: under vs undo
These two trip readers on the page rather than in the ear: under is /ˈʌndə/ while undo is /ʌnˈduː/. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 letter(s) in length, and the parts of speech differ too (preposition vs verb), which is usually the fastest check. Our composite confusion score for this pair is 13811, derived from the frequency rank of both members and their visual similarity.
under is recorded at frequency rank #180, classified as aprep, pronounced /ˈʌndə/. undo is at rank #13,631, tagged as averb, pronounced /ʌnˈduː/.
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 13811, this pair ranks #473,705 of 530,003 scored English confusable pairs - a relatively easy-to-tell-apart pair.
Orthographic DNA of under vs undo
Shared letters: dnu. Private to "under": er. Private to "undo": o.
"under" · 5 letters · shape VCCVC · "undo" · 4 letters · shape VCCV
Known mistypes of this pair
Frequently Asked Questions
Can "under" and "undo" be used interchangeably?
In ordinary English text, does "under" or "undo" show up more?
After this comparison
Eye-level mix-up between "under" and "undo" is sorted above. Next: full entries or other pairs that share a letter shape.
- Full dictionary entry for "under" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "undo" - compare definitions side by side with the headword page. Word entry
- This pair ranks #473,705 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "under" and "undo" also get mixed up with nearby pairs, the highest-scored neighbour is "UHD vs undo". 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 #473,705 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.