by accident

Meaning

This phrase is used to describe something that happens unintentionally, without planning, or by chance. In academic contexts, it is often used to describe unexpected scientific discoveries (like penicillin) or unintentional errors in data collection or experiments. It is the opposite of 'on purpose' or 'deliberately'.

Examples

• Penicillin was discovered by accident when Alexander Fleming noticed mold growing in a petri dish.

  Penicillin was discovered by accident when Alexander Fleming noticed mold growing in a petri dish.

• I deleted the database file by accident and had to restore it from the backup.

  I deleted the database file by accident and had to restore it from the backup.

• She found the rare manuscript by accident while searching the university archives.

  She found the rare manuscript by accident while searching the university archives.

• The researchers mixed the wrong chemicals by accident, leading to an unexpected reaction.

  The researchers mixed the wrong chemicals by accident, leading to an unexpected reaction.

• We met at the library by accident, as we hadn't planned to study together.

  We met at the library by accident, as we hadn't planned to study together.

Common Mistakes

• ✗ The discovery was made on accident.

  ✓ The discovery was made by accident.

  While 'on accident' is common in informal American spoken English, 'by accident' is the standard, grammatically correct form preferred in academic and formal writing.

• ✗ I did it by accidental.

  ✓ I did it by accident.

  'Accident' is a noun. You must use the noun form after the preposition 'by', not the adjective 'accidental'.

Related Expressions

Practice

• The scientist made the breakthrough ___ while working on a different project.

  💡 It happened without planning or intention.

  Show answer

  by accident

• I submitted the wrong draft of my paper ___.

  💡 An unintentional mistake.

  Show answer

  by accident