本日|ほんじつhonjitsu[1]atamadaka (head-high)

1. noun, adverbtoday; this day
   あいにくですが本日ほんじつは予約よやくでいっぱいです。↗

   I'm sorry, today is fully booked.

• Synonym今日きょうNeutralThe everyday word for today and the most colloquial choice; 「本日」 is its polite counterpart for formal and business contexts, as in 「本日休業」.
• Antonym昨日きのうNeutralYesterday, the day before today; the opposite of 「本日」 in date order.
• Antonym明日あしたNeutralTomorrow, the day after today; the opposite of 「本日」 in date order.

In formal or business speech, say today with 「本日」, as in 「本日はお越しいただき」; in everyday conversation use 「今日」. The antonyms 「昨日」 and 「明日」 point to the day before and the day after.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 今いまが属ぞくしている日ひ。今日（きょう）きょうの漢語かんご的てき表現ひょうげんで、ややかしこまった言い方いいかた。