坂

1. Origins, structure, and basic meaning

• Structure: 坂(さか) is a noun for a slope or a road on an incline.
• Basic usage: It describes steepness in 急な坂 and serves as a route in 坂を上る or 坂を下る.

2. Common pitfalls and similar expressions

• Slope and movement
  • 坂 names the incline itself; 上る and 下る specify movement up or down it.
• Route particle
  • Use を when the slope is the route along which someone travels.