腰

1. Origins, structure, and basic meaning

• Structure: 腰 is read as こし and is a noun for the lower back or hip area.
• Basic usage: Hurting the lower back appears in 腰を痛める, while sitting well back in a chair appears in 深く腰を掛ける.

2. Common pitfalls and similar expressions

• Body part and sitting expression
  • 腰を掛ける is a set expression meaning to sit down.
• Difference from 背中
  • 腰 focuses on the lower back and hips rather than the back as a whole.