炭

1. Origins, structure, and basic meaning

• Structure: The fuel noun 炭 (すみ) denotes charcoal made by heating wood with limited air.
• Basic usage: It can be placed in a brazier to start a fire, and remaining charcoal is cleared away after cooling.

2. Common pitfalls and similar expressions

• Charcoal as material
  • It focuses on the fuel material itself, distinct from the charcoal fire while it is burning.