自動

1. Origins, structure, and basic meaning

• Structure: 自動（じどう） describes operation under set conditions without a person carrying out each operation.
• Basic usage: It applies not only to machines but also to devices such as lights that respond to a condition.

2. Common pitfalls and similar expressions

• Two ways to modify an action
  • 自動で in the first example and 自動的に in the second both indicate that the following action happens automatically.
• Contrasting control methods
  • 手動 means operation controlled directly by a person. 自動 means operation under set conditions, so the two contrast methods of control.