three days and three nights
A set phrase emphasizing a continuous period of three full days and nights. Often used in storytelling or dramatic contexts.
He worked for three days and three nights without sleeping.
The river flooded after three days and three nights of rain.
Means 'one whole day and night', a similar construction for a single 24-hour period.
Compound of 三日 (three days) and 三夜 (three nights). The reading みっか is the native Japanese counting form for three days, and みよ is the corresponding form for three nights.