How to say "day" in Japanese

• デーCommon
  suffixA borrowed word for the 'day' of holidays and other specially named days. It is not the general word for a day; for counting or referring to ordinary days, use 日.
  ボクシング・デイは、郵便ゆうびん屋やさんや牛乳ぎゅうにゅう屋やさんなどに贈り物おくりものをする日ひですが、クリスマス後ごの最初さいしょの週日しゅうじつです。↗

  Boxing Day, when presents are given to the postman, the milkman, etc., is the first week-day after Christmas.
• 日にちひにちJLPT N2approx.Common
  nounThe word for the date of a planned event or action: use it when arranging, asking about, or changing when something will happen. It can also mean a day in the ordinary sense.
  会合かいごうの日ひにちと場所ばしょが決定けっていされた。↗

  The date and place of the meeting have been fixed.
• 日ひJLPT N4approx.Common
  nounThe basic word for a day as a unit of time: one day, several days, or a particular day on which something happens. For the ordinary calendar sense, this is the default choice.
  この服ふくは寒さむい冬ふゆの日ひには向むかない。↗

  These clothes are not appropriate for a cold winter day.

For days as units of time or particular days use 日, for the date of a planned event use 「日にち」, and for the 'day' of holidays and specially named days use 「デー」.

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

• デーday (as in holiday)
• 日にちひにちdate (of a planned event, act, etc.)
• 日ひday