落ちる

1. Origins, structure, and basic meaning

• Structure: 落ちる, read おちる, is an intransitive verb for falling downward or for a value or level decreasing.
• Basic usage: It describes a book falling from a shelf and also a reduction in speed with 速度が落ちる.

2. Common pitfalls and similar expressions

• Physical falling and a drop in level
  • It covers a book physically falling and a vehicle's speed decreasing. The subject and context show what kind of downward change is meant.