雷雲

1. Origins, structure, and basic meaning

• Structure: 雷雲 is a noun read らいうん, meaning a thundercloud capable of bringing thunder and lightning.
• Basic usage: Use 雷雲が広がる for it spreading across the sky and 雷雲が近づく for its approach.
  • 西の空に黒い雷雲が広がってきた。 describes a dark thundercloud spreading across the western sky; 雷雲が近づいたので屋外の作業を中止した。 describes stopping outdoor work because the thundercloud approached.

2. Common pitfalls and similar expressions

• 空に雷雲が広がる
  • に marks the area of sky, while が marks the thundercloud.
• 広がってきた
  • てきた presents the cloud's spreading as approaching the speaker's view or the present.
• 近づいたので
  • ので gives the approaching thundercloud as the reason for stopping work.