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See also: -undo



Etymology 1[edit]

From Middle English undōn, from Old English ondōn, 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) (transitive)

  1. To reverse the effects of an action.
    Fortunately, we can undo most of the damage to the system by the war.
    • 1610–1611 (date written), William Shakespeare, “The Tempest”, in Mr. William Shakespeares Comedies, Histories, & Tragedies [] (First Folio), London: [] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act I, scene ii], page 4:
      Pro. [] it was a torment / To lay vpon the damn'd, which Sycorax / Could not againe vndoe ; it was mine Art, / When I arriu'd, and heard thee, that made gape / The Pyne, and let thee out.
    • 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, Caleb Quinley, “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.
    Could you undo my buckle for me?
  3. (figuratively) To impoverish or ruin, as in reputation; to cause the downfall of.
Derived terms[edit]


undo (plural undos)

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

Etymology 2[edit]



  1. Misspelling of undue.

Further reading[edit]


  1. ^ undo”, in OED Online Paid subscription required, Oxford, Oxfordshire: Oxford University Press, launched 2000.




From unda (a wave).



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

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


   Conjugation of undō (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,
pluperfect undāveram undāverās undāverat undāverāmus undāverātis undāverant
future perfect undāverō undāveris undāverit undāverimus undāveritis undāverint
passive present undor undāris,
undātur undāmur undāminī undantur
imperfect undābar undābāris,
undābātur undābāmur undābāminī undābantur
future undābor undāberis,
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 undāverīmus undāverītis undāverint
pluperfect undāvissem undāvissēs undāvisset undāvissēmus undāvissētis undāvissent
passive present under undēris,
undētur undēmur undēminī undentur
imperfect undārer undārēris,
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 undātūrum esse undārī undātum esse undātum īrī
participles undāns undātūrus undātus undandus
verbal nouns gerund supine
genitive dative accusative ablative accusative ablative
undandī undandō undandum undandō undātum undātū

Derived terms[edit]


  • Aromanian: undedz, undari
  • English: undate
  • Italian: ondare
  • Portuguese: undar
  • Romanian: unda, undare
  • Spanish: ondear


  • undo”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
  • undo”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
  • undo in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette
  • Carl Meißner; Henry William Auden (1894) Latin Phrase-Book[3], London: Macmillan and Co.
    • a thing finds credence, is credible: aliquid fidem habet (vid. also fides under sect. VII., History)
  • redound”, in The Century Dictionary [], New York, N.Y.: The Century Co., 1911, →OCLC.




  1. flattery