Quick answer
Undo is a verb meaning to reverse or unfasten something. Undue is an adjective meaning excessive or not justified. Example: you can undo your last edit, but you would not want to put undue pressure on anyone.
The core difference
Undo is a verb for reversing something, while undue is an adjective meaning excessive or unjustified.
- undo — to reverse, unfasten or ruin something: You can undo your last edit with Ctrl+Z.
- undue — more than is reasonable, or not justified: There is no need for undue alarm.
How to tell them apart
Check the job the word does. If it is an action, something you do to a knot, an edit or a mistake, use undo. If it describes a noun such as pressure, delay, influence or haste, use undue.
The mix-up shows up because the words sound almost the same. Try replacing the word with excessive. If the sentence still works, you want undue. If you can swap in reverse or unfasten, you want undo.
Frequently asked questions
Is it undue influence or undo influence?
It is undue influence. Undue is the adjective, meaning improper or excessive, and it describes the noun influence.
Can undo be a noun?
Yes, especially in software, where undo is a command that reverses the previous action. Every good text editor supports undo.
Is undue related to due?
Yes. Undue is un- plus due, so it means not due, in the sense of not justified or more than is reasonable.
