替え

1. Origins, structure, and basic meaning

• Structure: 替え is a noun read かえ, meaning a replacement or spare used in place of the original item.
• Basic usage: It can refer to replacement batteries kept in a drawer or a spare pair taken out after socks become wet.
  • 電池の替えを引き出しに入れておいた。 says that replacement batteries were kept in the drawer; 雨で靴下が濡れたので替えを出した。 says that a spare pair was taken out because the socks got wet in the rain.

2. Common pitfalls and similar expressions

• 電池の替え
  • の identifies batteries as the items for which replacements were prepared.
• 替えを出す
  • The preceding reference to wet socks supplies the omitted noun, so 替え means a spare pair of socks.
• 替え and 予備
  • 替え is an item ready to replace the original, while 予備 broadly denotes something reserved in advance for possible need.