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Nihongo Online School > Tips for More Effective Studying > How to Say “Why … ?” in Japanese | どうして〜んですか (doushite ~n desu ka) | JLPT N4 Grammar
How to Say “Why … ?” in Japanese | どうして〜んですか (doushite ~n desu ka) | JLPT N4 Grammar
2025/10/30
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The expression “〜んです” (and its question form “〜んですか”), one of the most natural ways to explain reasons or situations in Japanese.
Compared with “どうして〜ですか” or “〜ませんか”, the question “どうして〜んですか” sounds more natural and is used far more often in conversation. Native speakers usually prefer “どうして〜んですか” because it sounds softer, more natural, and fits perfectly in spoken Japanese when asking about someone’s actions or circumstances.
Contents
When and How It’s Used
The pattern “Q. どうして〜んですか / A. 〜んです” is used when you want to ask or explain the reason or background for an action.
When someone asks you with “どうして〜んですか,” you respond with “〜んです” to explain the reason or circumstances.
This form is similar to “〜からです”, but it feels lighter and more conversational.
It’s common in spoken Japanese, but not used in formal writing.
See How It’s Used in Conversation
This video will help you understand how どうして〜んですか is used in everyday Japanese conversations. Watch and repeat to improve your listening and speaking skills!
Sentence Pattern
普通形 (plain form)＋んです
- Verbs: たべる → たべるんです／たべない → たべないんです
- i-adjectives: さむい → さむいんです
- na-adjectives & nouns: きれい → きれいなんです／学生 → 学生なんです
★Q.どうして～んですか。 ―Why〜？<Ask the reason or circumstances>
A.～んです。 ーBecause〜．<Explain reason or circumstances>
This pattern adds a gentle, explanatory tone rather than simply stating facts.
Examples
Q: どうしてケーキを食べないんですか。 Dōshite kēki o tabenain desu ka.
A: 今、ダイエットをしているんです。 Ima, daietto o shite irun desu.
Q: Why aren’t you eating cake?
A: I’m on a diet.
→ Explains the reason for not eating cake in a friendly way.
Q: どうして会社を休んだんですか。 Dōshite kaisha o yasundan desu ka.
A: 頭が痛かったんです。 Atama ga itakattan desu.
Q: Why did you take a day off from work?
A: I had a headache.
→ Describe the personal situation naturally.
Even without being asked “どうして〜んですか,” you can still use “〜んです” to explain your situation politely.
Q: 昨日日本語を勉強しましたか。 Kinō nihongo o benkyō shimashita ka.
A: いいえ、昨日はアルバイトだったんです。 Iie, kinō wa arubaito dattan desu.
Q: Did you study Japanese yesterday?
A: No, I had a part-time job yesterday.
Q: 仕事が終わったら映画を見に行きませんか。 Shigoto ga owattara eiga o mi ni ikimasen ka.
A: すみません。今日は約束があるんです。 Sumimasen. Kyō wa yakusoku ga arun desu.
Q: Want to go to a movie after work?
A: Sorry, I already have plans today.
In Summary
The pattern “〜んです” lets you explain things naturally and politely.
It makes your Japanese sound softer, more empathetic, and closer to native speech. Use it when you want to show your situation or reason gently — and you’ll instantly sound more fluent and natural.
Enhance your JLPT N4 with Nihongo Online School
Mastering the core grammar of JLPT N4 is just one step toward passing the exam. To build a solid foundation, you’ll also need to learn JLPT N4 Grammar List , and also Play List on Youtube for JLPT N4 helps you understand important grammar easily.
At Nihongo Online School, our programs combine vocabulary, grammar, and practical usage in a clear, structured way, designed to help you succeed on the JLPT N4. With our learning system giving you the confidence and preparation you need for the exam.Discover your favorite courses at Nihongo Online School .