What is the difference between 日{ひ} and 一日{いちにち}? I thought that 一日 was used when refering to the length of a day but I saw this sentence and got confused:


Also, on the news this morning the announcer said that it would probably become a beautiful day.

Why is it correct to use 一日 rather than 日 here? Thanks.


2 Answers 2


The concept of a day is quite ambiguous in any language and Japanese is no exception. A day can be: 24 hours, a calendar day, a period between sunrise and sunset, a period between you wake up and go to sleep, one's workday. One day might have more than 24 hours (長い一日だった), the other less...

That said 一日{いちにち} in your example refers to a time period that someone perceived or might perceive as a "beautiful day". It is essentially 一日間 here and although using it would be unnatural, it would probably be grammatical.

Like in 忙しい一日でした the 間 is absent, but if you extended the period to two weeks you would say 忙しい2週間でした.

日{ひ} on the other hand has more of a "calendar day" or an "exemplary day" feeling to it. うららかな日は外で遊びます。


一日 means either the first day of the month or one day, but can also mean all day.

In that context, 一日 is used to denote that the whole day will be beautiful.

Anyone please correct me if I'm wrong, I'm still learning myself.

  • tsuitachi = first day of the month but Ichinichi means "[that] one [entire] day" .. you're right =)
    – sova
    Commented Oct 25, 2015 at 19:38
  • At work you can say「今日も一日宜しくお願いします」 but hopefully it refers only to business hours... ;)
    – macraf
    Commented Oct 25, 2015 at 22:21
  • So would it be incorrect to change 一日 to 日? Commented Oct 26, 2015 at 0:15

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