なぜ知っているの？How do you know?

Hi everyone,

There is a common mistake (よくあるミス) that many English conversation students make in class: Saying "Why do you know?" instead of "How do you know?" Although 「なぜ」 is, indeed, "Why" in English, native speakers do not use it for this question. If you look it up in the dictionary (辞書で調べたら), you will see that "How" can be 「どうして」　and 「どうやって」.
So, please think of the question in the following way:
どうして［どうやって］それが分かった[を知っている]のですか。
If you do, then it will be easier to remember to use "How" instead of "Why" at the beginning of the sentence. How do I know that?
Because I'm a native speaker! (ネイティブやけん[きん]！).

See you at E-Style,

Alan