砂時計

1. Origins, structure, and basic meaning

• Structure: 砂時計 (すなどけい) is a noun for an hourglass or sand timer that measures time by falling sand.
• Basic usage: It describes turning over a timer to measure a set period or sand falling through one.
  • 三分の砂時計を返して時間を計った。 — I turned over a three-minute hourglass to measure the time.
  • 机の上の砂時計から細かな砂が落ちている。 — Fine sand is falling through the hourglass on the desk.

2. Common pitfalls and similar expressions

• Actions used to measure time
  • 砂時計を返す describes turning the hourglass over, while 時間を計る describes measuring time with it.