雷

1. Origins, structure, and basic meaning

• Structure: The single-kanji word 雷 is read かみなり and can refer to thunder or to a lightning strike.
• Basic usage: The sense is clarified by its verb: 雷が鳴る concerns thunder sounding, while 雷が落ちる concerns lightning striking.

2. Common pitfalls and similar expressions

• Thunder and a lightning strike
  • In the first context it refers to thunder as a sound, while in the second it refers to lightning striking a tree. The surrounding event determines which sense is intended.