螺旋階段

1. Origins, structure, and basic meaning

• Structure: The spelling is 螺旋階段, read as らせんかいだん. It is a noun for a staircase that winds around a central axis in a spiral between levels.
• Basic usage: Climbing a spiral staircase appears in 螺旋階段を上る, while referring to the central spiral staircase appears in 中央の螺旋階段.

2. Common pitfalls and similar expressions

• Difference from 階段
  • It specifies a winding spiral form rather than stairs in general.