Translation guide
Expresses the idea of 'all the time', 'continuously', or 'around the clock'. Japanese uses set phrases and adverbs rather than a direct translation of 'day and night'.
To say that something happens without stopping, 24 hours a day.
Literally 'day and night', used as an adverb meaning 'continuously' or 'around the clock'. Common in both spoken and written Japanese.
He works day and night.
Literally 'both day and night', used adverbially to mean 'all the time'. Slightly more conversational than 日夜.
She studies day and night.
Means 'regardless of day or night', 'around the clock'. Often used in formal or written contexts.
Literally 'four six hours all the time' (4×6=24), meaning 'around the clock'. Somewhat old-fashioned or emphatic.
To compare or contrast daytime and nighttime, not necessarily continuous action.
Simple noun phrase meaning 'day and night' as two distinct periods. Use when contrasting them.
English 'day and night' often means 'all the time'. Translating it literally as 昼と夜 (day and night) in such contexts sounds unnatural. Use 日夜 or 昼も夜も instead.
This shop is open day and night.
He plays games day and night.
The temperature differs greatly between day and night.
More formal or technical way to say 'daytime and nighttime'. Used in weather forecasts, schedules, etc.
Please be careful of the temperature difference between day and night.