The past simple and the past participle of undo

Conjugation of the verb undo:

Base Form/Infinitive without 'to':


Past Simple:


Past Partciple:


Present Partciple:


Third Person Singular:



1. To to reverse the effects of an action that happened earlier.
2. To unfasten, loosen, untie.
3. To cause the ruin, downfall, or the impoverishment of.


1. One must find a way to undo the damage of holiday eating.
2. He loosened his tie and undid the buttons of his shirt.
3. He was a famous politician who was undone by scandals.

Similar verbs

The irregular verbs in the table below have the same pattern as undo. They are:

- Verbs that are different from all the other patterns.
- Verbs like 'be, was/were, been'.

Verb Simple past Past Participle
be was/were been
do did done
go went gone
lie lay lain
saw sawed sawed/sawn
sew sewed sewed/sewn
show showed shown
sow sowed sown/sowed
strew strewed strewed/strewn
underlie underlay underlain
undo undid undone
unedrgo underwent undergone