substitute · generation

1. Origins, structure, and basic meaning

• Structure: 代 relates to substitution or succession and is read だい in 代理 and 時代.
• Basic usage: 代理 means acting on someone else's behalf; 時代 means an era or period with particular characteristics.

2. Common pitfalls and similar expressions

• Acting in someone's place
  • 父に代わって店番をする means to run the shop in one's father's place.
  • 代わる is read かわる; 代える, replacing something with a substitute, is read かえる.
• The span of an era
  • 祖父が若かった時代 refers to the time when one's grandfather was young.
  • The span of 時代 depends on context, not necessarily one generation or a fixed number of years.