なんで

「なんで」 means 'why' and is the spoken form, used with close friends, family, peers and younger people. Its feeling is direct, often puzzlement or surprise and sometimes a complaint: 「なんで？」 (Why on earth?). Do not use it in formal situations or business e-mail, or with elders and bosses; even 「なんでですか」 is not appropriate.

•Easy to mishear: 「何で行きますか」 read 「なんで」 can mean 'why are you going?' or 'how are you going?' (by what means). Context and intonation tell you.

•With a teacher or client, do not say 「なんでですか」; say 「どうしてですか」, or more formally 「なぜでしょうか」.