碁石

1. Origins, structure, and basic meaning

• Structure: 碁石 (ごいし) is a compound noun for the black and white stones used on a Go board.
• Basic usage: 黒い碁石を置く concerns placing one black stone at the board’s center, while 白と黒の碁石を戻す concerns returning stones of both colors to separate containers.

2. Common pitfalls and similar expressions

• Number comes from context, not noun form
  • 碁石 does not change form for singular or plural. 黒い碁石を置いた concerns one stone, whereas 白と黒の碁石 concerns multiple stones, so number comes from context.