This is the 8714th most frequent Japanese word.
昼夜
Day and night.
昼夜 is used to indicate the span of both day and night, emphasizing continuous effort.
彼は昼夜を問わず働いています。
He works tirelessly day and night.
昼夜 is used to compare the conditions observed during the day versus those at night.
昼夜で気温が大きく変化します。
The temperature changes significantly between day and night.
昼夜 is employed to describe the inversion between daytime and nighttime in the context of a habitual schedule.