時計

1. Origins, structure, and basic meaning

• Structure: 時計 (とけい) is a noun for an instrument that measures and displays time.
• Basic usage: 壁の時計が正午を知らせる makes a wall clock the source of a noon signal, while 腕時計の時刻を合わせる adjusts the displayed time before departure.

2. Common pitfalls and similar expressions

• Instrument type and displayed time
  • 壁の時計 and 腕時計 differ in placement, while 時計の時刻 is the value the instrument displays. The clock and time itself should not be treated as the same noun.