GrammarJLPT N5
なんで
→ why?
Why? / What for? / How? (By what means?)
JLPT N5AdverbCasual spoken
何で (なんで) is a casual interrogative adverb most commonly used to ask "why?" or "what for?" in everyday spoken Japanese. It functions similarly to なぜ and どうして, but sits at the most casual end of the formality spectrum, making it natural in conversations with friends and family but generally inappropriate in formal writing or polite business settings. In addition to asking about reasons, 何で can also be read as なにで and used to ask about means or method — "by what means?" or "how?" — where で functions as the particle indicating means or instrument (e.g., "What did you come by?"). Context and intonation usually make the intended meaning clear: when asking about reasons, it is pronounced なんで, and when asking about means, it is typically pronounced なにで, though in casual speech the distinction can blur. Compared to なぜ, which is formal and often literary, and どうして, which is neutral and polite, 何で (なんで) is the go-to choice for informal, direct questioning about reasons.
Functions
#1 Asking for a reason (why / what for)
Structure
なんで + Sentence?
なんで昨日学校に来なかったの？
Here なんで is used at the beginning of the sentence to ask for the reason behind someone's absence. This is the most common usage of 何で and is typical of casual, spoken Japanese. The sentence-ending の adds a tone of curiosity or mild insistence, which pairs naturally with なんで in informal conversation. A more polite equivalent would be どうして or なぜ.Why didn't you come to school yesterday?
Structures
- Asking why (reason)
- なんで + Sentence (+ の / んですか)?
- Asking by what means
- なにで + Verb?
Common mistakes
Learners often confuse the two readings of 何で: なんで (why) and なにで (by what means). Mixing these up can lead to misunderstandings — for instance, answering a "why" question with a mode of transportation, or vice versa. Another common error is using なんで in formal situations such as business emails or polite conversations with superiors, where なぜ or どうして would be far more appropriate. Additionally, some learners use なんで interchangeably with どうやって (how / in what way), but どうやって asks about process or procedure, while なにで asks specifically about the tool or means used. Finally, forgetting to add の or んですか at the end when asking for reasons can make the sentence sound abrupt or unnatural, even in casual speech.
Related
なぜどうしてどうやって何どう