一 日(いちにち)

いちにち

noun

one day, all day

1. one day (duration)

A period of 24 hours or one full day.

How many hours do you work in one day?

I spent one day in Tokyo.

The trip will end in one day.

This work won't be done in one day. It takes about three days.

I thought it would be done in one day, but it took two days.

2. all day, the whole day

Throughout an entire day from morning to night.

一日(いちにち)中(じゅう)雨(あめ)でした。

It rained all day.

一日中 = all day long

一日(いちにち)中(じゅう)本(ほん)を読(よ)んでいました。

I was reading books all day long.

I stayed at home all day on Sunday.

The children were playing outside all day long.

I caught a cold, so I was sleeping all day.

Please rest for the whole day.

一日(いちにち) refers to a period of one day or, with 中(じゅう), means 'all day long.'

READING NOTE:
When meaning 'the first day of the month,' this word is read 一日(ついたち), not いちにち.

COMMON PATTERNS:

DURATION COUNTING:

For counting days as a duration, Japanese uses the native number system:

The suffix 間(かん) is optional for 一日(いちにち) but typically added for other counts (二日間(ふつかかん), 三日間(みっかかん)).

basic

Added 2026.1.7 21:40 · Revised 2026.5.14 0:16

00500/00942_ichinichi