何故

1. Origins, structure, and basic meaning

• Structure: 何故 (なぜ) is an interrogative adverb used to ask for or frame a reason.
• Basic usage: 何故黙っていたのか asks the reason for remaining silent, while 何故この道を選んだのか frames an explanation of a choice in one’s own words.

2. Common pitfalls and similar expressions

• Direct force and embedded question
  • 何故黙ったのか and 何故選んだのか both form clauses asking for a reason. Neither must be a direct question demanding an immediate answer from another person.