# undo

> English word · Verb · IPA /ʌnˈduː/ · frequency rank #13,631

## Definitions
1. To reverse the effects of an action.
2. To unfasten.
3. To unfasten the clothing of (a person).
4. To impoverish or ruin, as in reputation; to cause the downfall of.

## Etymology
From Middle English undōn, from Old English ondōn, from Proto-West Germanic *andadōn (“to undo”), equivalent to un- + do. Cognate with West Frisian ûndwaan, ûntdwaan (“to undo; rid”), Dutch ontdoen (“to undo”).

## Easily confused with
- **UO** (https://plainspell.com/en/vs/undo-vs-uo)
- **USD** (https://plainspell.com/en/vs/undo-vs-usd)
- **uni** (https://plainspell.com/en/vs/undo-vs-uni)
- **uno** (https://plainspell.com/en/vs/undo-vs-uno)
- **utd** (https://plainspell.com/en/vs/undo-vs-utd)
- **USO** (https://plainspell.com/en/vs/undo-vs-uso)
- **unit** (https://plainspell.com/en/vs/undo-vs-unit)
- **unto** (https://plainspell.com/en/vs/undo-vs-unto)
- **USDA** (https://plainspell.com/en/vs/undo-vs-usda)
- **Unix** (https://plainspell.com/en/vs/undo-vs-unix)
- **Urdu** (https://plainspell.com/en/vs/undo-vs-urdu)
- **univ** (https://plainspell.com/en/vs/undo-vs-univ)
- **UNLV** (https://plainspell.com/en/vs/undo-vs-unlv)
- **union** (https://plainspell.com/en/vs/undo-vs-union)
- **undue** (https://plainspell.com/en/vs/undo-vs-undue)
- **undone** (https://plainspell.com/en/vs/undo-vs-undone)
- **UD** (https://plainspell.com/en/vs/ud-vs-undo)
- **und** (https://plainspell.com/en/vs/und-vs-undo)
- **UFO** (https://plainspell.com/en/vs/ufo-vs-undo)
- **Una** (https://plainspell.com/en/vs/una-vs-undo)

## Common misspellings (5)
`nudo`, `udno`, `unddo`, `unndo`, `unod`

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/undo