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PlainSpell

undo

/ʌnˈduː/verb, noun

undo is spelled U-N-D-O: 4 letters and 2 syllables. It appears 3.7 times per million words in written English, the 13,496th most frequent word form (wordfreq, 2021 data). People search “undo vs undue” about 50 times a month (Google, United States). As a verb, undo means “To reverse the effects of an action” (English Wiktionary, September 2026).

How many letters and syllables are in undo?

Letters4: U-N-D-O
Syllables2 (from its American pronunciation)
In writing3.7 times per million words; the 13,496th most frequent word form
Wrong spellings searchednone measured in search
Pairs people search
Sounds like
Rhymes with
Same letters

Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation and the CMU Pronouncing Dictionary; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media); Bing searches in the United States: the average month from September 2025 to August 2026 (Microsoft Advertising keyword data through DataForSEO, read September 30, 2026); rhymes and same-letter words are computed by PlainSpell from its own word list.

How common is undo?

Undo appears 3.7 times per million words in written English, the 13,496th most frequent word form in the list.

Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).

How do you pronounce undo?

  • US /ʌnˈduː/

Undo has 2 syllables (counted from its American pronunciation in the CMU Pronouncing Dictionary).

Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Recordings: LL-Q1860_(eng)-Vealhurl-undo.wav, Wikimedia Commons (author and licence on each file's page).

Words people confuse with undo

Word pairs people search, with the monthly searches for “a vs b” (G: Google, B: Bing, United States).

undo vs undue50 G

Sounds like: undue (Wiktionary's homophone list; some hold only in some accents).

Sources: Google and Bing searches (September 2025 to August 2026, through DataForSEO); English Wiktionary (homophones, alternative spellings).

What rhymes with undo?

The 12 most written words on PlainSpell end in the same sounds as undo from its last stressed vowel (/u/):

Spelled with the same letters in another order: udon.

Computed by PlainSpell from the pronunciations in the English Wiktionary (dump of September 2, 2026): a rhyme shares every sound from the last stressed vowel to the end; ordered by written frequency (wordfreq 3.1).

Forms of undo

  • undoes present, singular, he/she/it
  • undoing participle, present
  • undid past
  • undone participle, past
  • undos plural

Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).

What does undo mean?

The meanings the English Wiktionary records, quoted as written there (source below).

verb

  1. 1

    To reverse the effects of an action.

    Fortunately, we can undo most of the damage to the system by the war.

  2. 2

    To unfasten.

    Could you undo my buckle for me?

  3. 3

    colloquialTo unfasten the clothing of (a person).

    PROSTITUTE: Undo me. There's a dear.

  4. 4

    To impoverish or ruin, as in reputation; to cause the downfall of.

noun

  1. 1

    An operation that reverses a previous action.

    How many undos does this program support?

Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).

Undo in Spanish, French, German and Portuguese

LanguageWords
Frenchannuler, défaire (to reverse), délier (to unfasten)
Germanrückgängig machen, ungeschehen machen (to reverse), aufmachen, öffnen, losmachen, lösen (to unfasten)
Portuguesedesfazer (to reverse), desatar (to unfasten)
Spanishdeshacer, desfacer, dirimir (to reverse)

Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Translations are Wiktionary's, by sense; a linked word has its own PlainSpell page.

Where does undo come from?

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”).

Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).

What to look up after undo