んだ・んです

    • だ/です
    んだ and its variants such as んです add an explanatory feel to a sentence. It’s often used to provide information in order to fill the gap of understanding.

    Table of Contents

    The Basics

    んだ and its variants (んです/のだ/のです) usually come at the end of a sentence and add an explanatory feel to the sentence. The basic function of these is to fill the gap of understanding between a speaker and a listener. So you often use them to explain something or resolve misunderstandings. Using one makes the sentence sound as if you are trying to share the piece of information in order to fill in the blanks, often it’s some context that your listener is missing.

    An example? Let’s say today is your lucky day — you unintentionally impressed your date by helping out an Italian tourist who was lost. Your date didn’t know you could speak Italian so they look surprised and confused. In this situation, you may say something like:

    • 実はイタリアで育ったんだ。
    • (It’s because) I actually grew up in Italy.

    Simply saying 実はイタリアで育った without adding んだ still gives the same information, but it doesn’t sound quite as natural and may come off as a random statement. On the other hand, adding んだ creates a natural flow for you to complete the context by explaining why you can speak Italian, which is something your date is obviously wondering. So even though it’s not a universal translation, the nuance んだ adds in this case is almost like “It’s because…” Whether or not your date explicitly asks why you speak Italian, it’s natural to use んだ in this case.

    Still cloudy? That’s understandable. Although it’s a common expression, it has a very unique and subtle nuance and there’s no exact translation in English. So keep reading to observe more examples to deepen your understanding!

    Patterns of Use

    んだ and its variants are made out of the same set of two components. The first part is the particle の (nominalizer). This の often changes to ん especially in spoken Japanese, and that’s why you see variations like んです or んだ. The second part is です and , which are very common sentence enders in Japanese. With that in mind, let’s take a look at how you can form a sentence with them.

    With Verbs

    Like we mentioned earlier, the first part of んだ is the nominalizer の. So if you are familiar with how verbs interact with the nominalizer の, you might already know how you can attach んだ to verbs. For those who are not sure, don’t worry, it’s quite simple with verbs. You can use pretty much any form of verb, like present form, passive form, potential form, negative form, you name it. Then you simply attach んだ (or its variation) at the end.

    Present Form

    • 勉強するんだ。
    • I study.

    Past Form

    • 勉強したんだ。
    • I studied.

    Passive Causative Form

    • 勉強させられたんだ。
    • I was made to study.

    You can use any form of a verb as long as it’s to explain how an action is performed or how an event happens. However, verb forms like the command form or volitional form won’t work as they don’t make sense for explanations.

    ❌ 勉強しろんだ。

    Another thing to note is that it only works with the plain form as opposed to the polite form, aka the ます-form.

    ❌ 勉強しますんだ。

    If you want to be polite, んです would be a good option for you!

    勉強するんです。

    With い-Adjectives

    い-Adjectives work with んだ similarly to the way the nominalizer の works with it. Since the nuance んだ adds is explanatory, it usually combines with a form of い-Adjectives that explains the way of things, like the present tense, past tense, and negative form.

    Present Form

    • 悲しいんだ。
    • I’m sad.

    Negative Form

    • 悲しくないんだ。
    • I am not sad.

    Past Negative Form

    • 悲しくなかったんだ。
    • I wasn’t sad.

    い-Adjectives should be in the plain form, not in the polite form.

    ❌ 悲しいですんだ。

    With Nouns And な-Adjectives

    So far, it’s been very simple as we’ve been just attaching んだ to sentences and words. However, you might want to pay closer attention with nouns and な-adjectives. For example, to say “I’m a vegetarian,” you use the noun, ベジタリアン (vegetarian) and say:

    • ベジタリアンなんだ。
    • I’m a vegetarian.

    …Did you notice something is a bit different? You need to insert な after a noun. And, this is the same for other な-adjectives as well. To say “it’s easy,” you use a な-adjective, 簡単 (easy), and say:

    • 簡単なんだ。
    • It’s easy.

    What about if you wanted to say “I was a vegetarian“ or “It isn’t easy”? To show different a tense, or whether it’s a positive or negative sentence, you use the conjugation forms of .

    Past Form

    • ベジタリアンだったんだ。
    • I was a vegetarian.

    Negative Form

    • 簡単じゃないんだ。
    • It isn’t easy.

    In case you were wondering why we added な to the present form instead of だ — that’s because historically, な comes from だ. Crazy, right? But hopefully that explains why we use it with both nouns and な-adjectives (which are noun-based adjectives). Both of these can also precede だ to form a sentence.

    んだ for Explaining

    Adding an explanatory tone is one of the most common features of んだ. We already saw an example of んだ being used for this purpose earlier. In the previous example, you humblebragged about why you speak Italian after you unpurposefully impressed your date with your Italian skills, saying:

    • 実はイタリアで育ったんだ。
    • (It’s because) I actually grew up in Italy.

    Your date was obviously wondering why you could speak Italian, so you used んだ to fill in the gap of understanding between you and them by providing information about the circumstance. Let’s take a look at another example. You are still on the date, and later on, you run into a familiar face. It’s a crowded place so you briefly exchange greetings and part ways. Whether your date actually asks you or not, again they are wondering “Who was that?” So to fill in the blank, you use んだ and say:

    • 同じレストランで働いてたんだ。
    • We worked at the same restaurant.

    Now you see how んだ is being used again to fill in the gap of understanding between you and your date? Without んだ, it still conveys the same piece of information, but it could sound like a random statement that came from out of the blue, while んだ creates a smooth flow by making it clear that you are explaining something.

    んだ for Resolving Misunderstandings

    んだ can be used to fill in the gap of understanding between you and your listener not only when your listener is missing some information, but also when they’re misunderstanding something. For example, your sister is upset because her favorite ice cream (that she even put her name on) is now gone. You know how upsetting that is, right? She is somehow convinced that you ate it and is falsely accusing you of eating her ice cream. However, you know it was actually your mom who ate it. So to exonerate yourself, you use んだ and say:

    • 違うよ、お母さんが食べたんだよ。
    • No, mom ate it.

    Just like that, you can use it to provide information to resolve a misunderstanding. You’ll often see the sentence ending particle paired up with this んだ. They match up well because よ indicates you’re trying to offer a new perspective that your listener does not have.

    Beyond The Basics

    んだ And んですか for Realization

    So far, we’ve seen examples of んだ being used when you explain something to someone else, but it can also be used for your own realization as if you’re explaining something to yourself. In this case, んだ indicates that you were not previously aware of the information, and you filled in the blank yourself. Let’s say your roommate looks very happy today. You ask if something good happened to him. Turns out he’s just got promoted. In a response to that exciting information, you can say:

    • 昇進したんだ。おめでとう!
    • You got promoted. Congrats!

    Just like that, んだ can show that you’re realizing something as if you’re explaining it to yourself while processing the information.

    In a situation where you’re using んです, which is more polite, you’ll need to add a question marker, か. This makes it more of a confirming question, rather than explaining something to yourself and processing the information on your own. If it was your father-in-law who got promoted (not your roomie), for example, you might say something like:

    • 昇進したんですか。おめでとうございます!
    • Did you get promoted? Congratulations!

    There are also cases when you don’t have a particular listener at all, like when you’re talking to yourself. For that kind of situation, んです is not so suitable because です is used for social situations. However, んだ would be perfect as its ending part is more self-directed. Let’s take a look at an example. On a different occasion, your roomie looks kind of down and locks himself in his room. You’re wondering why. Then you see his very emotional post on social media and you find out that he had his heart broken. You may say to yourself (in your mind or say it aloud — I won’t judge you):

    • そっか、フラれちゃったんだ…。
    • I see, he got dumped…

    んだ is perfect to express realizations with the nuance of “Oh, gotcha” because you use it when the gap of understanding is filled. It’s like you put the puzzle pieces together yourself.

    の And んですか For Seeking Explanation

    んだ can also be used for asking for an explanation or a request to fill in the blank in the form of a question. And in real-life conversations, the variants, の and んですか, are most commonly applied for this use. We mentioned it briefly in the previous section, but んですか is a combination of んです and the question marker, か).

    Now let’s see how it works in action. For example, one day when you come back to work from a lunch break, all of your coworkers are freaking out and you don’t know why. You ask someone:

    • 何かあったんですか? (Polite)
      何かあったの? (Casual)
    • Has something happened?

    In this case, you want to use の or んですか as you’re seeking an explanation of why everyone is panicking. You sense that something is wrong, but you don’t know what. So you’re asking your coworkers to fill in the blanks for you. And when someone explains the reasoning, they might use んだ (or its variants) back to you as they’re filling in the gap of understanding. They may say something like:

    • ゴキブリが出たんです。(Polite)
      ゴキブリが出たんだ。 (Casual)
    • There’s a cockroach.
      (Literally: A cockroach appeared.)

    Ew, a cockroach!? Yikes, but it all makes sense now why everyone is freaking out!

    んだ For Introducing A New Topic

    We’ve seen examples where んだ gets used for explanation when something is unclear — there’s a gap in understanding that needs to be filled. For example, your friend might call you and say:

    • 今日は会えない。風邪ひいちゃったんだ。ごめんね。
    • I can’t see you today. I caught a cold. I’m sorry.

    This is the good ol’ んだ at play. You were probably wondering why your friend wasn’t able to meet up with you today, so they explained it to you. But, this order can also be a little different — you can use んだ as a way of starting a conversation by sharing the context first.

    • 風邪ひいちゃったんだ。 だから今日は会えない。ごめんね。
    • I can’t see you today. I caught a cold. I’m sorry.

    With んだ, your listener can expect some sort of relevant statement coming. That way, んだ can be a good way of introducing a new topic, or starting a conversation.

    Different Forms of んだ — んです / のです / のだ

    As we’ve mentioned, んだ has a few variants, namely, んです, のです and のだ, and there are nuanced differences between them.

    First of all, the ones with ん (んだ and んです) have a colloquial feel to them, like when の is changed to the ん sound to make it easier to say. You will also see this in casual writing, like texts, emails, blog posts and such. However, for more formal writing, the ones with の (のだ and のです) are usually prefered.

    • 明日、海に行くんだ。
    • I’m going to the beach tomorrow.

    The other components are です and だ. To put it simply, です is a politeness marker, and what that means is, んです is sort of semi-casual. It’s politer than んだ, but still colloquial. You might use it to talk to someone you don’t know well or want to be polite with in conversation.

    • 明日、海に行くんです。
    • I’m going to the beach tomorrow.

    のです, on the other hand, sounds a bit stiff or overly polite when it’s used in conversation, but you would see it in casual readings like blogs or novels.

    • 母は最初ケンイチの結婚に反対したのです。
    • Kenichi’s mother disapproved of his marriage at first.

    だ is an assertiveness marker. The nuance is casual when it’s used in conversation, especially when paired up with a sentence ending particle like よ and ね, or in the form of んだ. It’s also self-directed while です is social. This explains why んだ can be used as-is for expressing realization. のだ is very assertive, so you would likely find it in formal writing like academic papers. It’s rarely used in real-life conversation, but it’s sometimes used to portray anime characters as confident or arrogant.

    • カリフォルニア州は小売店でのビニール袋の使用を禁止した最初の州なのだ。
    • California was the first state to prohibit the use of plastic bags for retail.

    んだ For Commands

    You can also use んだ for commands, for when you’re trying to fill in a gap of understanding between you and the person you’re talking to — like when they’re not taking things seriously, for example. When んだ is used for commands, it’s typically seen when dramatising situations in movies and novels. Let’s use a typical action movie scene as an example. There’s a ticking bomb right in front of you and your sidekick. You have to run as quickly as you can, but your sidekick is shocked by fear and freezes. You yell at them and say:

    • 逃げるんだ!
    • Run!

    Using んだ like this is kind of a movie cliché, as the example may have sounded like. And, compared to the regular command form 逃げろ, which simply tells the sidekick to run, 逃げるんだ sounds more dramatic, as if you’re really trying to get the sidekick to understand the situation (and how serious and life-threatening it is)!

    While you might not see んだ being used like this in real-life too often, you’ll likely see it being used in actual conversation, especially when the sentence ending particle is added. For example, when your son is leaving to start living on his own for the first time. As a parent, you might say something like:

    • ちゃんと毎日朝ごはん食べるんだよ。
    • You eat breakfast everyday, okay?

    This probably comes from you knowing your son’s habit of skipping breakfast. You’re worried about him and you use んだよ to express that you’re wanting him to understand he should eat breakfast everyday.


    Now that you've finished reading about んだ and its variants, it's time to review what you've learned on this page! Listen to this podcast episode to solidify your knowledge on this topic.