decay

1. Origins, structure, and basic meaning

• Structure: 朽 has 6 strokes and refers to material rotting or something losing strength and declining.
• Basic usage: 朽ちる is read くちる, and 不朽 is read ふきゅう.

2. Common pitfalls and similar expressions

• Decay and lasting value
  • 木材が少しずつ朽ちていった describes wood gradually rotting. The verb also applies to a country declining from within, as in 王国が内側から朽ちる.
  • 不朽の名作 is an enduring masterpiece whose value lasts across generations. Adding 不 expresses freedom from decay.