腐る

1. Origins, structure, and basic meaning

• Structure: 腐る is read as くさる and is a verb meaning to rot or spoil and, figuratively, to become discouraged or sulk after a setback.
• Basic usage: Literal decay appears in 果物が腐る, while discouragement appears in 失敗くらいで腐ってはいけない.

2. Common pitfalls and similar expressions

• Literal and figurative senses
  • It can describe actual decomposition in food or figuratively portray a person losing heart.
• Difference from 腐らせる
  • 腐る is intransitive: something rots or someone becomes discouraged. 腐らせる is transitive and means to cause something to rot.