What does undo mean?
Undo is a common verb meaning to reverse, cancel, or counteract an action or its effects. It is used when a decision must be reversed, when a change must be erased, or when damage or disruption must be repaired: one might undo an edit, undo a cancellation, or undo the damage caused by an accident. In computing, undo is especially familiar as the command that restores the previous state after an action, although modern applications may offer clearer alternatives such as revert or restore. The word is neutral in register and can be used in everyday conversation, formal writing, technical contexts, and figurative expressions. Its usefulness lies in its direct contrast with doing: it names the deliberate reversal of an action rather than merely stopping it. The related form undone can describe work that has been undone, as well as a task that remains incomplete.
To reverse or cancel an action, effect, or change; to restore something to a previous state.
"You can undo the formatting and return the text to its original style."
Common in literal, figurative, and computing contexts. The object may be an action, a change, an effect, or damage.
An act or operation of reversing a previous action, especially in computing.
"The undo command brought the document back to its earlier state."
This noun use is uncommon and most often appears in computing or in descriptions of reversible operations.
The countable plural is uncommon; the noun is usually encountered in computing contexts or as part of a phrase such as an undo command.
"Several undos in the editing history showed how the document had been revised."
In computing, undo reverses a previous action, while redo applies it again—an everyday verb pair built on one small prefix.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does undo come from?
The English verb undo was formed in the late 16th century by combining the prefix un- with do, giving it the basic sense of reversing or undoing an action. The prefix un- continues Old English un-, meaning “not” or “opposed to,” while do comes from Old English dōn, “to do, perform, or carry out.” The form undone later became established both as a past participle and as an adjective meaning reversed, incomplete, or ruined.
Related word forms
How undo is actually used
The verb is neutral in register and common in both everyday and technical contexts. It can suggest literally reversing an action, as in editing software, or more broadly cancelling consequences. The noun use is uncommon and is especially associated with computing and formal descriptions of reversible operations.