I'm frequently encountering English proofreading problems. For now I am trying to figure out which one of these two is the correct form: in purpose or on purpose. I tried to Google and found both forms used in various web-pages. If both of these forms are correct, please explain when which one is better to use.

2 Answers 2


on purpose is what's used. This is a legitimate expression in English with its own entry in the dictionary. It means intentionally. I myself use it all the time. As for the other one, I have never ever heard anyone say in purpose in place of on purpose. That would just sound wrong.

However, you could say in purpose in certain situations, but that would mean a totally different thing. For example:

This thing is completely useless in purpose as well as in use.

Meaning, it for whatever reason does not have a purpose and thus is considered useless.

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    Thank you very much. I vote up your answer. I need just some points to make my up-votes visible. I believe the answers of native English speakers, but here I found this phrasal verb in this online dictionary: thefreedictionary.com/In+purpose I guess this dictionary contains wrong data as well
    – iwlpe
    Nov 16, 2017 at 8:58
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    Read carefully what that dictionary says: On purpose is the form now generally used. Nov 16, 2017 at 9:02
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    note: the opposite phrase is technically "by accident", not "on accident", though "on accident" is often used informally
    – Mike B
    Jun 12, 2021 at 21:00

on purpose is correct. the other way to say this could be “for the purpose of (x), they did (y). “

examples: “He was upset with his brother, so he burnt his toast on purpose.” or “for the purpose of grading the tests faster, the teacher decided to have the students work in groups during class.”

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