故意

1. Origins, structure, and basic meaning

• Structure: 故意 (こい) marks action performed knowingly and intentionally. 故意に modifies an action, while 故意の limits the character of a following noun.
• Basic usage: 故意に壊した concerns whether the vase was broken on purpose; 故意の反則 records a judgment that a foul was deliberate.

2. Common pitfalls and similar expressions

• Adverbial 故意に and attributive 故意の
  • Adverbial に scopes over 壊した; attributive の classifies 反則. A reading of accident or chance would reverse the intended meaning.