open

1. Origins, structure, and basic meaning

• Structure: The on reading is かい, and the kun readings are ひらく, ひらける, あく, and あける. It has 12 strokes. It appears in words for opening something and something opening.
• Basic usage: 開く can also be read ひらく; the selected entry for a door or store opening is read あく.

2. Common pitfalls and similar expressions

• 開ける / 開く
  • 開ける means open and is read あける. It describes a person opening a window or box.
  • 暑いので窓を開けてもいいですか。 means “May I open the window because it is hot?”
  • 開く means open and is read あく. It describes train doors or a store opening.
  • 電車の扉が開くまで黄色い線の内側で待った。 means “I waited behind the yellow line until the train doors opened.”