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See also: -undo




Etymology 1Edit

From Middle English undōn, from Old English undōn, ondōn (to undo; undo that which is open; close; release; absolve; abrogate; destroy), from Proto-Germanic *andadōną (to undo), equivalent to un- +‎ do. Cognate with West Frisian ûndwaan, ûntdwaan (to undo; rid), Dutch ontdoen (to undo).


undo (third-person singular simple present undoes, present participle undoing, simple past undid, past participle undone)

  1. To reverse the effects of an action. ant. syn.
    Fortunately, we can undo most of the damage to the system by the war.
    • 2011 October 15, Michael Da Silva, “Wigan 1 - 3 Bolton”, in BBC Sport[1]:
      But Wigan undid their good work by conceding an avoidable second goal deep into first-half injury time.
    • 2019 April 6, Quinley, Caleb, “Thailand: Anti-military party leader faces sedition charges”, in Al Jazeera[2], Doha: Al Jazeera, retrieved 2019-04-06:
      And judging by how well the progressive and youth-favoured party did, many observers suspect this latest round of legal charges are a response to Future Forward's commitment to undo the legacy of military rule and undertake democratic reforms.
  2. To unfasten. ant. syn.
    Could you undo my buckle for me?
  3. (figuratively) To impoverish or ruin, as in reputation; to cause the downfall of.


undo (plural undos)

  1. (computing) An operation that reverses a previous action.
    How many undos does this program support?

Etymology 2Edit



  1. Misspelling of undue.

Further readingEdit


  1. ^ “undo”, in OED Online  , Oxford: Oxford University Press, launched 2000.




From unda (a wave)



undō (present infinitive undāre, perfect active undāvī, supine undātum); first conjugation

  1. I rise in waves.
  2. I overflow with, abound in.
  3. I wave, undulate.


   Conjugation of undo (first conjugation)
indicative singular plural
first second third first second third
active present undō undās undat undāmus undātis undant
imperfect undābam undābās undābat undābāmus undābātis undābant
future undābō undābis undābit undābimus undābitis undābunt
perfect undāvī undāvistī undāvit undāvimus undāvistis undāvērunt, undāvēre
pluperfect undāveram undāverās undāverat undāverāmus undāverātis undāverant
future perfect undāverō undāveris undāverit undāverimus undāveritis undāverint
passive present undor undāris, undāre undātur undāmur undāminī undantur
imperfect undābar undābāris, undābāre undābātur undābāmur undābāminī undābantur
future undābor undāberis, undābere undābitur undābimur undābiminī undābuntur
perfect undātus + present active indicative of sum
pluperfect undātus + imperfect active indicative of sum
future perfect undātus + future active indicative of sum
subjunctive singular plural
first second third first second third
active present undem undēs undet undēmus undētis undent
imperfect undārem undārēs undāret undārēmus undārētis undārent
perfect undāverim undāverīs undāverit undāverimus undāveritis undāverint
pluperfect undāvissem undāvissēs undāvisset undāvissēmus undāvissētis undāvissent
passive present under undēris, undēre undētur undēmur undēminī undentur
imperfect undārer undārēris, undārēre undārētur undārēmur undārēminī undārentur
perfect undātus + present active subjunctive of sum
pluperfect undātus + imperfect active subjunctive of sum
imperative singular plural
first second third first second third
active present undā undāte
future undātō undātō undātōte undantō
passive present undāre undāminī
future undātor undātor undantor
non-finite forms active passive
present perfect future present perfect future
infinitives undāre undāvisse undātūrus esse undārī undātus esse undātum īrī
participles undāns undātūrus undātus undandus
verbal nouns gerund supine
nominative genitive dative/ablative accusative accusative ablative
undāre undandī undandō undandum undātum undātū

Derived termsEdit






  1. flattery