前線

1. Origins, structure, and basic meaning

• Structure: 前線, read ぜんせん, denotes a battlefront or a boundary between air masses with different properties.
• Basic usage: In 寒冷前線が近づき、空が急に暗くなった。, a cold front approached and the sky suddenly darkened.

2. Common pitfalls and similar expressions

• War and weather
  • The 前線 that soldiers head toward is a battlefront; 寒冷前線 is a cold front in weather.