一段

1. Origins, structure, and basic meaning

• Structure: 一段(いちだん) can count one step or level, or indicate a further degree.
• Basic usage: It describes moving up one stair and a change such as the cold becoming more severe.

2. Common pitfalls and similar expressions

• Quantity and degree
  • 一段上がる means going up one step; 一段と厳しい means even more severe.
  • The following と and an expression of degree help distinguish this from counting physical steps.
• One occasion and one step
  • 一回 counts one occurrence, whereas 一段 can count one division in stairs or height.