～んです can be difficult for Japanese learners to use correctly. Grammatically, it’s easy to use it: ～んです simply just comes after the dictionary form of a word, and it always comes at the end of a sentence or phrase. So what makes it so problematic for learners? The answer is that ～んです has a social function, so the trick is knowing when it’s appropriate to use it.
4. 要求／願望（しばしば要求や願望が間接的に提示されることもあり）: Requests / Desires (sometimes expressed indirectly)
Related to #4, sometimes「んですが、～」 is spoken after the person says what they want and before they ask a related question. To make the request more polite, のですが can be used like this:「(desire) のですが、 (question)」。
- Person A : 「Bさん、このレストランに行きたいのですが、どうですか？」
- “B-san, I’d like to go to this restaurant. What do you think?”
- Person B : 「いいですよ。」
- “That’s fine.”
Sometimes speakers omit the question after saying んですが, but the listener usually understands the implied question, as in the example below.
(At a summer festival)
- Child (outside a candy apple cart, looking at the candy apples): 「お母さん！お母さん！これ食べたいんだけど！」 （買ってくれない？）
- “Mom, mom! I want to eat this!” (Implied: So will you buy it for me?)
- Mother : 「ダメ！」
The child’s sentence trails off after 食べたいんだけど (“I want to eat this!”), but the mother understands what’s been omitted from the sentence--“So will you buy it for me?”--and responds to the question implied by the child. Of course, some listeners might be impatient and prefer the speaker to make the request outright. For example, a different mother might say, 「だから何？」 (“And…? So what?”) to make the child directly express what he or she wants.
The set phrase といいんですが is often used to signal what the person wants to happen, as seen below. Sometimes this usage is translated as “I hope…”
- “I have a date tomorrow. I hope it doesn’t rain. I wonder if it will be okay.”
Japan is also a high-context culture, so a lot of meaning and information is communicated indirectly. You have to pay attention to the surrounding context to understand what’s been omitted. The following two examples both involve using ～といいんですが in the context of passing an exam, but for different reasons: humility versus. uncertainty. The listener has to pay attention to the context, the speaker’s intonation, and his or her knowledge of the speaker to understand why the speaker trailed off.
- Person A : 「今回の試験ちょっと難しかったね。」
- “This exam was a little difficult, right?”
- Person B : 「そうだね。試験に合格するといいんだけど、、、。」（でもダメかも。)
- “Yeah. It’d be good if I passed, but…” (Implied: Maybe I did badly.)
- Person A : 「でも、Bさんは頭が良いから絶対大丈夫だよ。」
- “But, you’re smart so I’m sure you did fine.”
In this situation, there is a high probability that Person B is being humble. Person A recognizes this because he or she is paying attention to the context.
- Person A : 「〜さん、今度JLPTN5のテストだね。」
- “~san, after this is the JLPT N5 test, right?”
- Person B : 「そうです。テストに受かるといいんですが、、、。」（でも、たぶん受からないと思います）
- “That’s right. It’d be good if I pass the test, but…” (Implied: I think I might not pass.)
- Person A : 「どうしたの？自信がないの？」
- “What’s wrong? You’re not confident?”
- Person B : 「はい。あまり自信がありません。」
- “Yes. I don’t have much confidence.”
This situation is similar, but this time Person B is using といいんですが from a lack of confidence, not from humility. (As a quick note, notice that Person A’s use of 「...の？」 in this conversation matches usage #1: Explanation).
To understand what a sentence ending in といいんですが is signaling, you must pay attention to the context. In this final example, it’s not signaling humility, uncertainty, or an implied desire. Instead, the exact same phrase has the function described in the previous section (#3: To Preface), and it can be translated simply to mean “but...”
- Person A : 「試験はどうだったんだ？」
- “How was the test?”
- Person B : 「まあまあでした。」
- “It was okay.”
- Person A : 「受かるといいな。」
- “It’d be good if you passed.” (i.e., “I hope you passed.”)
- Person B : 「受かるといいんですが、このテストはそんなに重要ではないのであまり気にしていません。」
- “It’d be good if I passed but, this test isn’t very important so I don’t care that much.”
- Person A : 「そうか。」
- “Oh, I see.”
In some situations, んだ is added to the end of a verb’s dictionary form to become a strong command to do that action. This is masculine speech, so women usually don’t use this. It’s also a command, not a polite request, so be careful when using んだ in this way.
- “You understand, right? If you understand, then start working right away.”
In this example, 働くんだ is a direct order to another person to work, much like the conjugation 働け (“go work!”). For comparison, the て form, like 働いてください (polite) or 働いて (casual) is used when you’re requesting someone to do something, not ordering them to do it.