undo

/ʌnˈduː/ (bre, ipa) · /ʌnˈduː/ (ame, ipa) · /ˌən-ˈdü ˈən-/ (ame, mw)

undo — verb

  • undopresent simple I / you / we / they
  • undoeshe / she / it
  • undidpast simple
  • undonepast participle
  • undoing-ing form

1. to release or separate something that has been closed, tied, or fastened — like

1.動詞及物B1
釋義

to release or separate something that has been closed, tied, or fastened — like untying a shoelace, unbuttoning a shirt, or unzipping a jacket.

例句

Yasmin carefully undid the knot in her necklace chain with her fingernails.

undo + concrete physical object (knot)

The toddler undid every button on his shirt before his mother could stop him.

同義詞
  • unfasten

    more formal and general; works for any kind of fastening

  • untie

    specific to knots, laces, or ribbons

  • loosen

    suggests making less tight rather than fully opening

  • unbutton

    specific to buttons only

反義詞
  • fasten

    general opposite — to close or fix something in position

  • tie

    specific to laces, ropes, or ribbons

文法句型

undo + noun phrase (concrete object: button, knot, shoelace, zipper)

用法筆記

Object is always a concrete fastening device (button, knot, zipper, lace, buckle, tie) or a garment that has such a fastening. Not used for opening a container by lifting a lid or pulling a tab — use 'open' for those.

常見錯誤

❌She undid the box to find her phone.
✅She opened the box to find her phone.
💡undo means releasing a fastening, not opening a lid or flap.
❌He undid the bottle by twisting the cap.
✅He opened the bottle by twisting the cap.
💡undo only applies to fastenings like buttons, knots, ties, or zippers.

2. to cancel or roll back whatever happened as a result of something someone did, b

2.動詞及物B1
釋義

to cancel or roll back whatever happened as a result of something someone did, bringing things back to how they were earlier — for example, cancelling a change on a computer or making up for harm done in a relationship.

例句

Inês knew that no apology could undo the hurt caused by her unkind words.

undo + abstract noun (hurt, damage, effect)

Christopher panicked when he realised he could not undo the message he had just sent.

同義詞
  • reverse

    more formal; often used in technical or legal contexts

  • cancel

    focuses on preventing the effect from continuing

  • nullify

    formal; suggests making something legally or officially void

  • rectify

    formal; implies correcting an error or problem

反義詞
  • cause

    to make something happen, the opposite of reversing an effect

  • do

    the general verb for performing an action that might later be undone

文法句型

undo + noun phrase (abstract effect, action, or change)

用法筆記

Object is usually an abstract noun describing the consequence of an action (damage, harm, change, mistake, effect). In computing, 'undo' is a standard command and the object can be the action itself (undo a deletion, undo a change).

常見錯誤

❌I undid the document from my computer.
✅I deleted the document from my computer.
💡undo reverses an action; delete removes an object.
❌She undid the meeting.
✅She cancelled the meeting.
💡undo is for reversing effects, not cancelling scheduled events.

3. to cause the failure, collapse, or destruction of a person, plan, organisation,

3.動詞及物B2
釋義

to cause the failure, collapse, or destruction of a person, plan, organisation, or situation, often through a series of actions or a single decisive event.

例句

A single scandal undid twenty years of progress for the environmental group.

undo + abstract noun (progress, career, plans — cause ruin)

Wren's poor business decisions eventually undid everything her parents had built over decades.

同義詞
  • ruin

    more direct and common; suggests complete destruction

  • wreck

    stronger; implies violent or total destruction

  • sabotage

    implies deliberate harm, often secret or underhanded

  • destroy

    general; can apply to physical or abstract things

反義詞
  • build

    to construct or develop over time

  • strengthen

    to make something stronger, the opposite of causing failure

文法句型

undo + noun phrase (person, plan, career, organisation)

用法筆記

The object is always something that was built up over time (reputation, career, progress, fortune, plans). This sense carries a strong implication of a fall from a previous good state. Distinguish from sense 2 by noting that sense 2 is about reversing an effect (which could be neutral), while sense 3 is specifically about causing catastrophic failure or destruction.

常見錯誤

❌The storm undid the roof of the house.
✅The storm destroyed the roof of the house.
💡undo in this sense applies to abstract collapse (career, plans, reputation), not physical destruction.
❌His laziness undid his homework.
✅His laziness undid his chances of passing the class.
💡undo (sense 3) means destroying long-term progress, not simply failing to complete a single task.