How do you differentiate "nande" (why) and "nande" (how, by what means)?


In a question:

[code]

    Tokyo e nande ikimasu ka?
    
[/code]

how can I know what "nande" refers to, **even when I have the context** :

  * how are you going? (by bus, by car, on foot)
  * why are you going?




I'll attempt an answer with a few observations from my rather amateurish
position:

  * The sentence is rather stilted to begin with, you probably won't hear it used in practice.
  * 何で can be pronounced both _nande_ and _nani de_.
  * Usually you'll hear people use _nande_ for "why" and _nani de_ for "with what" or "by what means".
  * Usually sentences asking "why" _start_ with the "why":

> [何で]【Nande】[東京]【Tōkyō】に【ni】[行きます]【ikimasu】か【ka】？  
>  Why are you going to Tokyo?

  * It's _possible_ to use the same word order [何]【Nani】[で]【de】[東京]【Tōkyō】に【ni】… to ask "with what", but since written as 「何で」 it is indeed ambiguous whether it's 「[なに]【nani】[で]【de】」 or 「[なんで]【nande】」, you'll either find it unambiguously written in hiragana, or with furigana, or put entirely differently:

> [東京]【Tōkyō】に【ni】[行く]【iku】[に]【ni】[は]【wa】[何]【nani】[で]【de】[行きます]【ikimasu】か【ka】？  
>  About you going to Tokyo, _how_ are you going?

While it's _still_ possible to misread that, again, most "why" questions put
the 「[何で]【nande】」 at the start of the sentence, so it would be _unusual_ to
misread this.

  * Japanese always depends a lot on context, so usually the question should be clear from the relationship between the speaker and the listener and/or the situation. In spoken language the intonation can also give the right hint, e.g. 「[なあぁんで]【Naaande】[東京]【Tōkyō】[に]【ni】[行く]【iku】[の]【no】？！」 is probably more about the "why" than the "how"...
  * There are many ways to express this differently and less ambiguous as needed, e.g.: 
    * [行く方法]【ikuhōhō】 – means/way of going
    * [行く理由]【ikuriyū】 – reason for going
    * [飛行機]【Hikōki】[や]【ya】[新幹線]【shinkansen】[で]【de】[行きます]【ikimasu】[か]【ka】？ – Are you going by plane or train?

