合図

1. Origins, structure, and basic meaning

• Structure: 合図 (あいず) combines coordination 合 and sign 図 to denote a signal that prompts action or conveys readiness.
• Basic usage: It can start a race or be given by raising a hand when preparation is complete.

2. Common pitfalls and similar expressions

• A signal and the act of signaling
  • 合図で treats the signal as the cue, while 合図する describes producing the gesture or sound.