Irregular verb
The verb to undo
undo → undid → undone
B1Meaning: to open something tied or fastened; to cancel an action · Type: irregular · Frequency: Top 100 English verbs
Key points to remember
- Present Simple:
I/you/we/they undo·he/she/it undoes - Past Simple:
undid(like do → did) - Past participle:
undone - -ing form:
undoing
Conjugation of the verb to undo
Present Simple
| I | undo |
| You | undo |
| He / She / It | undoes |
| We | undo |
| You (pl.) | undo |
| They | undo |
Past Simple
| I | undid |
| You | undid |
| He / She / It | undid |
| We | undid |
| You (pl.) | undid |
| They | undid |
All the forms of the verb to undo
Present Simple
Full pageundo / undoes
“Press Ctrl+Z to undo.”
See the pagePresent Continuous
Full pageam / is / are undoing
“I am undoing the knot right now.”
See the pagePast Simple
Full pageundid
“He undid the knot.”
See the pagePast Continuous
Full pagewas / were undoing
“I was undoing the knot when the phone rang.”
See the pagePresent Perfect
Full pagehave / has undone
“I have already undone the knot.”
See the pagePast Perfect
Full pagehad undone
“She had already undone the knot when I arrived.”
See the pageFuture Simple
Full pagewill undo
“I will undo the knot tomorrow.”
See the pageGoing to Future
Full pageam / is / are going to undo
“I'm going to undo the knot this weekend.”
See the pageConditional (would)
Full pagewould undo
“I would undo the knot if I had time.”
See the pageHow to use to undo
1. Opening something (a button, a knot)
- He undid his shoelaces.
2. Cancelling an action
- Press undo.
3. Undoing something (figurative)
- You can't undo the past.
A common mistake
1. Undoed ❌
Undo works like do: undid in the Past Simple, undone as the past participle. I undid my laces.
What's next?
You can conjugate to undo. Now say it out loud.
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Frequently asked questions
What is the past simple of undo?+
The Past Simple of undo is undid. The past participle is undone. Undo = un- (a prefix that means the opposite) + do, so it follows do → did → done.
What does undo mean on a computer?+
Undo cancels your last action: Ctrl+Z on Windows, Cmd+Z on a Mac. You find it in almost every program. The opposite is redo (Ctrl+Y).
What does what's done is done mean?+
It is a saying: once something has happened, you cannot change it. You can't undo it means you can't go back. The idea is to accept what happened.
What does undone mean?+
Undone can mean open, not fastened: My buttons are undone. It can also mean not done: The work was left undone. In literary English, he was undone by his mistake means his mistake ruined him.
Is it undid or undoed?+
Undo = un + do. Because do is irregular, undo is irregular too. Never say undoed. It is the same for redo → redid → redone and overdo → overdid → overdone.
Updated on 12 November 2026 by the Big Challenge teaching team. Every year, more than 500,000 students across Europe take part in our English contest, created in 1999. Our teaching approach →
The Big Challenge · Updated on 12 November 2026 · Source: www.thebigchallenge.com/bl/academy/learn-english/verbs/undo
© The Big Challenge. Copying allowed for classroom use. Every year, more than 500,000 students across Europe take part in our English contest, created in 1999.