昼夜

1. Origins, structure, and basic meaning

• Structure: 昼夜 (ちゅうや) is a compound noun for day and night together, either as continuous time or as contrasting periods.
• Basic usage: 昼夜を問わず動く describes operation continuing regardless of time, while 昼夜の気温差 compares desert temperatures between day and night.

2. Common pitfalls and similar expressions

• Continuous operation and period contrast
  • 昼夜を問わず marks an uninterrupted span, whereas 昼夜の差 contrasts two periods. The compound does not mean a duration of two days.