灰

1. Origins, structure, and basic meaning

• Structure: 灰 is read as はい and is a noun for ash, the powdery solid material left after something burns.
• Basic usage: A residue appears in 白い灰が残る, while use in an experiment appears in 灰を水に混ぜる.

2. Common pitfalls and similar expressions

• Remaining material
  • It is the solid residue after burning, not the flame or airborne material produced during combustion.
• Difference from 煙
  • 煙 is smoke that spreads through the air while something burns; 灰 is the ash left afterward.