悔恨

1. Origins, structure, and basic meaning

• Structure: 悔恨 (かいこん) is a noun for deep remorse or regret over a past wrong.
• Basic usage: 過ちへの悔恨を記す makes remorse for a mistake the feeling written in a letter, while 深い悔恨が表情に浮かぶ makes regret the subject visible in a face.

2. Common pitfalls and similar expressions

• Object of remorse and outward sign
  • In 過ちへの悔恨, への identifies what the remorse concerns; 悔恨が浮かぶ says the feeling becomes visible in an expression. The expression itself is not the past wrongdoing.