階段

1. Origins, structure, and basic meaning

• Structure: 階段(かいだん) means stairs, a series of steps for moving up or down.
• Basic usage: It describes a route between floors or a means of access used instead of an elevator.

2. Common pitfalls and similar expressions

• を for a route and で for a means
  • 階段を駆け下りる highlights the route taken; 階段で上る highlights the means of going up. The particles connect the stairs from different perspectives.
• A floor and a single step
  • 一階(いっかい) is the first floor of a building; 一段(いちだん) is one step. Distinguish the units when counting steps and identifying the destination floor.