I've been meaning to ask this for a while.

What is the difference between these 3 words. I was taught they all mean "why", but obviously, being different words they convey different nuance and would be used in different situations.

What would be the difference between these 3 sentences and in what situations would they be used?


3 Answers 3


From dictionary@goo:

  • なぜ is for asking 理由 (reason/motive) and 原因 (cause).

  • どうして covers なぜ usage, plus 方法 (method/process). Also, there is additional usage as a strong way to refuse.

  • なんで covers なぜ and どうして usage, including the usage as a strong way to refuse.

So I guess どうして and なんで are interchangeable while なぜ has a smaller scope than the two. As for the nuance differences between どうして and なんで, my theory is by looking at the literal meaning of the word, どうして focuses on "how it is done" while なんで focuses on "by what means".


For なぜ:

Very very directly asks for a reason. (Which is why なぜ appears the rudest)

For when you really intend to be direct. "No bullshit, tell me the reason now".

For どうして:

Deconstructing どうして yields どう(which way/manner) + して(Verb conjunctive form of する)

  1. どうする (Which way/manner of doing?)

  2. どうして[X] (Which way/manner of doing did X come to be?) Which is functionally equivalent to "why" since you indirectly ask for a cause of [X]. Also functions as a "how" since you ask for the way/manner of doing it.

For 何で:

  1. 何 (What)

  2. で (Instrumental particle)

  3. 何で (By what means) Which is functionally equivalent to "how"

"how" is a specific concept separate from "why" but share some similarities:

Question: Why? - Type of Response: Reason, Cause, Use of Method(is a subset of Cause)

Question: How? - Type of Response: Method

Simple illustration of the slight overlap:

Why does it work? - It works because this method is being used.

How does it work? - It works through this method.


Following my above assessment of どうして performing both functions of "why" and "how" and 何で for a functionally equivalent "how",

I would say that 何で may be replaced with どうして but どうして may not always be replaced by 何で. (However I do not know enough about the difference in nuance between them.)

None of them does the exact same thing as なぜ though, なぜ's nuance is its directness.

  • 12
    Your answer gives one the idea that なんで always means "how" and never "why", which is not the case. There are many cases where なんで is used where it does not mean "by means of what?" at all. (In fact, when you do mean "by what means?", it's more common to say なにで rather than なんで.) I think it's similar to how we say "how come?" in English. And, as it happens, using なんで to mean "why" (as opposed to "how") is informal just as "how come?" is informal in English. Commented Oct 27, 2011 at 17:55
  • @Kef I agree, I've never seen なんで mean "how". In fact, during my study abroad program in Japan, I was taught that なんで is a very strong Osaka dialect. Commented Sep 16, 2012 at 3:49


ええっとですね皆様、気持ちよくわかります。なぜ、どうして、なんで の話。

【どれを使ってもいい例】 [examples you can use them interchangeably] なぜそうなるの?どうしてそうなるの?なんでそうなるの?

【きちんと使い分ける例】[examples where one is clearly better than others] "being here somehow lets me calm down for some reasons."

GOOD! ここにいると、なぜか自然と気持ちが落ち着く。

okay ここにいると、どうしてか自然と気持ちが落ち着く。

weird ここにいると、なんでか自然と気持ちが落ち着く。

また、漢字で書くと由来が分かります。 なぜ、は、昔の「なにゆえ」という表現の現代語です。

なにゆえ 何故

なぜ   何故

ね、同じでしょ?何がwhat, 故がcause, reason,だから、まとめて for what reason, っていう感じ。ナニユエは古風で侍とかが言う感じ、ナゼは現代風。


こども:ねーねー今日、どうぶつえんいこーよー  I wanna go to the zoo today....can we? can we?

おとな:今日いそがしーからだめ~!! Naw....I'm busy today...

Good! こども:なんでーなんでーなんでー      why why why!!

Okay  こども:どうしてどうしてどうしてー

weird こども:なぜなぜなぜー

ここが なぜー だとちょっと変。そういう言い方する子供いない。 どうしてー どうしてー は、OKだけど10さいより大きい感じ。9歳よし下の小さい子は なんでー

  • Wouldn't an adult say something like なぜだ なぜだ Commented May 3, 2021 at 10:23

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