なぜ and どうして both mean “why.” They are used to ask for reasons. どうして is more common in daily conversation; なぜ is a bit more formal. Key points: • なぜ = why (more formal) • どうして = why (casual/common) • Often answered with ～から (because) • Used at the beginning of questions Example: “どうして日本語を勉強しますか” means “Why do you study Japanese?” A common answer is “日本が好きだからです.” You can use either word in most situations. If you want to be polite, use どうして. If you want a slightly formal tone, use なぜ. Practice by asking simple questions about reasons: どうして学校へ行きますか, なぜ忙しいですか.