Translation guide
This English phrase asks about the cause or purpose behind an action or situation. In Japanese, the most natural way to ask 'for what reason' depends on formality and whether you are asking about cause, purpose, or motive. The most common equivalent is なぜ, but どうして and 何のために are also used in different contexts.
The speaker wants to know the reason or cause behind something, in a neutral or slightly formal tone.
The most direct and common translation for 'why' or 'for what reason'. Used in both spoken and written Japanese, but can sound slightly formal in casual conversation.
なぜ遅れたのですか。
For what reason were you late?
なぜそう思うのですか。
For what reason do you think so?
A more colloquial and emotional way to ask 'why'. Often used when the speaker is surprised, upset, or curious. Common in everyday speech.
どうして来なかったの？
For what reason didn't you come?
A literal translation of 'for what reason', but it sounds stiff and is rarely used in natural conversation. Mostly found in formal writing or translations.
何の理由で彼は辞任したのか。
For what reason did he resign?
The speaker wants to know the purpose or goal behind an action, often implying 'for what purpose' or 'what for'.
Directly asks 'for what purpose' or 'for the sake of what'. Very common and natural when questioning the goal or objective.
何のために日本語を勉強しているのですか。
For what reason are you studying Japanese?
何のためにそんなことをしたの？
For what reason did you do such a thing?
More explicitly asks about the objective or aim. Slightly more formal and direct than 何のために.
何が目的でここに来たのですか。
For what reason did you come here?
The speaker wants a reason in a very informal, friendly, or blunt way.
The most common casual way to say 'why' or 'for what reason'. Used extensively in daily conversation among friends and family.
なんでそんなこと言うの？
For what reason do you say that?
なんで行かないの？
For what reason aren't you going?
なぜ is neutral/formal and common in writing. どうして is more emotional and conversational. なんで is very casual and can sound blunt if used in formal situations. Choose based on your relationship with the listener and the setting.
なぜ遅刻したのですか。（丁寧）
For what reason were you late? (polite)
どうして遅刻したの？（やや感情的）
Why were you late? (slightly emotional)
なんで遅刻したの？（カジュアル）
Why were you late? (casual)
The phrase '何の理由で' is a direct translation of 'for what reason' but sounds unnatural in most contexts. Use なぜ, どうして, or 何のために instead.