教訓

1. Origins, structure, and basic meaning

• Structure: 教訓(きょうくん) means a lesson or moral learned from experience, failure, or a story and applied to future conduct.
• Basic usage: It is used when treating a failure as a lesson for the next plan or identifying the moral of a folktale. Typical patterns are 失敗を教訓とする and 昔話に教訓がある.

2. Common pitfalls and similar expressions

• See it as the outcome of experience or a story
  • It is not mere information but guidance drawn from an event or narrative for use in later judgment.
• Difference from 反省
  • 反省(はんせい) is the process of reflecting on one's conduct, while 教訓 is the lesson retained from that reflection or event.