報いる

1. Origins, structure, and basic meaning

• Structure: 報いる(むくいる) means responding to help, trust, or similar support with a fitting action.
• Basic usage: It is used for repaying long-standing support with results or trying to live up to a benefactor's expectations.

2. Common pitfalls and similar expressions

• How repayment differs from 返す
  • お金を返す describes returning money, while 信頼に報いる means acting in a way that lives up to the expectations of someone who trusted you.