(こい)

こいに
adverb
intentionally; deliberately; on purpose
formallegaldescriptive
1. intentionally; deliberately; on purpose
Performing an action with full awareness and intent, as opposed to doing it by accident or mistake.
故意(こい)やったない
I didn't do it on purpose.
He was deliberately hiding information.
If you deliberately violate the rules, severe penalties will be imposed.

A formal adverb used to express that an action was done on purpose. 故意(こい) is a noun meaning "intent, deliberateness" and makes it adverbial. It is particularly common in legal, news, and formal written contexts.

Common collocations

Similar words

  • わざと — on purpose, deliberately (more colloquial; used in everyday speech)
  • 意図的(いとてき) — intentionally (similar formality; focuses on the planned nature)
  • 意識的(いしきてき) — consciously, intentionally (emphasizes awareness)

Usage

故意(こい)に is more formal and written than わざと. In legal contexts, 故意(こい) (as a noun) contrasts with 過失(かしつ) (negligence): 故意(こい)よる犯罪(はんざい) (intentional crime) vs. 過失(かしつ)による犯罪(はんざい) (crime by negligence).