当日

1. Origins, structure, and basic meaning

• Structure: 当日 is a noun read とうじつ, meaning the very day on which a scheduled event or activity takes place.
• Basic usage: It is common in instructions about payment on an event day or meeting arrangements on a travel day.
  • 参加費は催しの当日に受付で払います。 says that the participation fee is paid at reception on the day of the event; 旅行当日は朝早く駅に集合してください。 asks participants to meet at the station early on the day of the trip.

2. Common pitfalls and similar expressions

• 催しの当日に
  • の identifies which event the day belongs to, and に marks the payment time.
• 旅行当日は
  • Direct attachment to the preceding noun presents the day of the trip as the topic.
• 当日 and 前日
  • 当日 is the day of the event itself, while 前日 is the preceding day.