1.
how many days — asking about or referring to an unspecified number of days
Used to ask about the duration of something in days, or to vaguely refer to 'some number of days'. Formed from the question word 何 and the counter 日.
2.
what day (of the month) — asking the date of the month
When paired with the date, 何日 asks for the day of the month (the 1st, 2nd, 3rd, etc.). Context or an accompanying word such as 今日 makes this meaning clear.
Question word formed from 何 ('what, how many') + 日 (counter for days / day of the month). Which sense applies depends on context.
Usage
- Sense 1 (duration): often paired with 間 to explicitly mean 'for how many days', as in 何日間.
- Sense 1 (vague): 何日か means 'several / a few days' when not a direct question — the か turns it into an indefinite expression.
- Sense 2 (date): asks the day of the month. The answer uses the standard day-of-month readings (一日, 二日, ..., 二十日, 三十一日, etc.).
Common collocations
- 何日かかる: to take how many days
- 何日間: for how many days
- 何日か: several days; a few days (indefinite)
- 何日前: how many days ago
- 今日は何日: what day (of the month) is today
Similar words
- 何曜日: what day of the week — asks the weekday (Monday, Tuesday, etc.), not the date.
- いつ: when — a more general 'when', without specifying duration or date.
- 何月: what month.
Watch out
Learners sometimes confuse 何日 with 何曜日. If you want to know 'Monday or Tuesday?', use 何曜日. If you want to know 'the 5th or the 6th?', use 何日.
Related Words
Compare:
何曜日 (what day of the week)
Compare:
何月 (what month.)
Related:
何年 (how many years, what year)
Compare:
幾日 (how many days)