空気

1. Origins, structure, and basic meaning

• Structure: 空気 is read くうき.
• Basic usage: It can refer either to the air people breathe or to the atmosphere or mood of a place or group.

2. Common pitfalls and similar expressions

• Physical air
  • 冷たい空気が入ってきた describes cold air physically coming inside.
• Figurative atmosphere
  • 重い空気が和らいだ means that a tense or heavy atmosphere eased.