By Accident vs. On Accident: Which Is Correct?
Quick Answer
By accident is the correct and standard phrase in English.
On accident is informal and not accepted in formal writing or grammar exams.
Explanation
The phrase by accident has been used in English for centuries. It means something happened unintentionally or without planning. The preposition by is used in many similar fixed expressions, such as by chance, by mistake, and by coincidence.
On accident is used informally in some regions of the United States, often by analogy with the phrase on purpose. However, the logic doesn't hold, on purpose and by accident are separate idioms that evolved independently, and they are not interchangeable opposites in terms of preposition.
โ BY ACCIDENT
- Standard and universally accepted
- Used in all registers (formal, informal, academic)
- Correct in written and spoken English worldwide
โ ON ACCIDENT
- Informal, limited to some American dialects
- Not accepted in formal writing or exams
- Considered nonstandard by most grammar guides
Why People Say "On Accident"
The most common reason is the analogy with on purpose. Since the opposite of "accidental" is "intentional" (or "on purpose"), speakers sometimes infer that the opposite of "on purpose" should be "on accident." This reasoning feels natural, but English idioms don't always follow logical patterns.
Remember this pattern:
- โ I did it on purpose. (intentionally)
- โ I did it by accident. (unintentionally)
- โ I did it on accident.
Examples
Related Expressions Using "By"
The preposition by is used in many idiomatic expressions similar to "by accident":
Frequently Asked Questions
Is "on accident" ever acceptable?
It is used casually in some American dialects, especially among younger speakers. However, it is not accepted in formal writing, academic essays, IELTS/TOEFL exams, or professional contexts. Always use by accident in writing.
What is the difference between "by accident" and "by mistake"?
Both mean something was done unintentionally. By accident often implies an unforeseen physical event (e.g., dropped something), while by mistake often implies an error in judgment or confusion (e.g., took the wrong bag).
Why do we say "on purpose" but "by accident"?
These are fixed idiomatic expressions that developed independently over time. English idioms don't always follow predictable patterns, and these two phrases simply use different prepositions. The key is to memorize them as fixed phrases.
Practice
Choose the correct preposition:
"I sent the email to the wrong person ___ accident." (by / on)