螺旋

1. Origins, structure, and basic meaning

• Structure: 螺旋 is read らせん and is a noun for a spiral shape that turns around an axis while advancing.
• Basic usage: It is used for forms that continue while turning, such as a spiral staircase or wire wound around a rod.

2. Common pitfalls and similar expressions

• Flat curves and three-dimensional forms
  • Depending on context, it can refer to a flat spiral or to a three-dimensional helix that progresses upward or downward.