深層

1. Origins, structure, and basic meaning

• Structure: 深層 is read as しんそう and means “deep layer” and “underlying cause”.
• Basic usage: It refers both to a physically deep ocean layer and to an underlying cause hidden beneath a problem.

2. Common pitfalls and similar expressions

• 海の深層 / 問題の深層
  • Use 海の深層 for a physical layer and 問題の深層 for an underlying cause.