every day and every night; day after day; daily
Emphasizes continuous repetition both day and night; often used in poetic or emphatic contexts.
I practiced day after day and night after night.
I think of her every day and every night.
日夜 also means 'day and night', but is more formal and often used in set phrases like 日夜努力する.
Standard modern spelling using kana for the suffix ごと.
Kanji spelling using 毎 for ごと; less common and may appear in literary or older texts.
Compound of 日 (ひ, 'day') + ごと ('every') + 夜 (よ, 'night') + ごと ('every'). The suffix ごと attaches to nouns to mean 'each' or 'every'.