undid

/ʌnˈdɪd/ (bre, ipa) · [ˌʌndˈɪd] /ʌnˈdɪd/ (ame, ipa) · [ˌʌndˈɪd] /ˌən-ˈdü How to pronounce undo (audio) ˈən-/ (ame, mw)

undid — verb

  • undidpresent simple I / you / we / they
  • undids3rd person singular
  • undidding-ing form
  • undiddedpast simple

1. the past simple form of the verb 'undo'

1.動詞A2
釋義

the past simple form of the verb 'undo'

例句

Felipe undid the lock on the gate with a paperclip and slipped inside.

past simple form of undo

Hana checked her work and undid the parts that did not look right.

用法筆記

Undid is the irregular past simple form of undo. The past participle is undone (e.g. 'The damage is undone'). This sense is a grammatical form label only; the specific meaning depends on context and is covered by the semantic senses below.

常見錯誤

❌Yesterday I undo my jacket.
✅Yesterday I undid my jacket.
💡use undid, not undo, for past actions.
❌She has undid her mistake.
✅She has undone her mistake.
💡use undone, not undid, after has/have/had.

2. to unfasten or untie something that is being held shut by a button, knot, zip, s

2.動詞及物B1
釋義

to unfasten or untie something that is being held shut by a button, knot, zip, strap, ribbon, or similar closure

例句

Marco undid the top two buttons of his shirt after the long meal.

undid + clothing fastening (button)

Saira carefully undid the knot in her necklace chain with a pin.

同義詞
  • unfastened

    more general — can apply to any type of fastening

  • untied

    specific to laces, ribbons, or strings

  • loosened

    suggests making something less tight rather than fully unfastening it

  • released

    often used for buckles, clips, or catches

反義詞
  • fastened

    the direct opposite

  • tied

    specifically for knots, laces, or ribbons

  • did up

    informal British English for fastening buttons or zips

文法句型

undid + noun (fastening/covering)

用法筆記

The object is usually a physical fastening: button, knot, shoelace, zip, buckle, strap, ribbon, belt, or seatbelt. Not used for general opening — you undo a fastened item, not a door or window.

常見錯誤

❌She undid the door and walked out.
✅She opened the door and walked out.
💡undid is for fastenings (locks, bolts), not for general opening of doors.
❌He undid his jacket by taking it off.
✅He undid the zip of his jacket and took it off.
💡undid refers to releasing the fastening, not removing the item.

3. to reverse the effect of an action or to make something no longer true or valid

3.動詞及物B2
釋義

to reverse the effect of an action or to make something no longer true or valid — for example, taking back a decision or fixing damage someone caused

例句

The new evidence undid the court's earlier decision on the case.

undid + abstract noun (decision)

Lucas undid months of training when he went back to his old eating habits.

同義詞
  • reversed

    suggests returning to a previous state

  • cancelled

    suggests an official or formal reversal

  • nullified

    more formal; suggests making something legally void

  • negated

    formal; suggests making an effect ineffective

反義詞
  • confirmed

    opposite of cancelling or reversing

  • enacted

    formal opposite of reversing a decision or law

  • did

    simple opposite of undoing an action

文法句型

undid + noun (effect/action)

undid what + clause

用法筆記

The object is usually an abstract noun: damage, harm, effect, progress, decision, change, or work. Also common with a what-clause: 'She undid what she had done.'

常見錯誤

❌He undid the TV by pressing the off button.
✅He turned off the TV.
💡undid is for reversing the effect of an action, not for switching devices on or off.
❌The teacher undid the student's answer.
✅The teacher crossed out the student's answer.
💡use cancel, erase, or delete for removing written answers.

4. to destroy someone's success, reputation, financial position, or future prospect

4.動詞及物C1
釋義

to destroy someone's success, reputation, financial position, or future prospects, often through a single damaging event or mistake

例句

The leaked emails undid the governor's hopes of running for president.

His reckless spending undid the fortune his grandmother had built over forty years.

undid + fortune / financial standing

同義詞
反義詞
  • built

    suggests constructing or developing

  • established

    formal opposite; creating a secure position

  • secured

    opposite of destroying someone's future or standing

文法句型

undid + person/reputation/career/future

用法筆記

This sense is more formal and literary than the others. The object is a person's achievements, future, or standing — never a physical object. Often found in news or narrative writing describing downfall.

常見錯誤

❌The rain undid our picnic.
✅The rain ruined our picnic.
💡undid in this sense is for serious destruction of life or reputation, not minor disappointment.
❌The child undid the tower of blocks.
✅The child knocked down the tower of blocks.
💡use knock down or break for physical objects.