Using んです for Explaining Things

    • Verb
    • Adjective
    • Noun
    んです indicates that something is said based on background information or knowledge shared between the speaker and the listener. For this reason, it adds an explanatory feel.

    Table of Contents

    What Is んです?

    んです is a grammar form that consists of two parts: ん and です. In more formal Japanese, and particularly in writing, の is used in place of ん. Using んです adds an explanatory nuance to a sentence, because it indicates that the statement being made is based on background information or knowledge shared by the speaker and the listener.

    んです can be used with nouns, adjectives, and verbs, but the way these words connect to んです is different, so we'll start by examining each.

    んです with Nouns and な-Adjectives

    To attach a noun or な-adjective to んです, we'll need to use the particle な. The pattern is the same for both of these word types:

    Word + な + んです = なんです

    So, we can add なんです to a noun, like 約束 (promise):

    約束 + な + んです = 約束なんです

    And just as easily, we can add なんです to a な adjective, like 綺麗きれい (beautiful):

    綺麗 + な + んです = 綺麗なんです

    Using な with a な-adjective probably seems straightforward, but why do we need it with a noun? As it turns out, な comes from だ, historically. Crazy, right? But that explains why we use it with both nouns and な-adjectives — both of these can also take だ to form a sentence!

    • 約束だ。 (noun)
    • It's a promise.
    • 綺麗だ。 (な-adjective)
    • It's beautiful.

    It's good to keep in mind that な and だ are kind of the same thing, because if you want to use a past tense or negative word with んです, you'll need to use variations of だ to get there. For example, use だった for past tense nouns and な-adjectives:

    • 約束だったんです。 (noun)
    • It's that it was a promise.
    • 綺麗だったんです。 (な-adjective)
    • It's that it was beautiful.

    Likewise, you can use negative forms, like じゃない or ではない to make the word negative:

    • 約束じゃないんです。 (noun)
    • It's that isn't a promise.
    • 綺麗ではないんです。 (な-adjective)
    • It's that it isn't beautiful.

    んです with い-Adjectives

    It's simple to add んです to い-adjectives — just attach it directly to the word. Let's check out some examples using 小さい (is small):

    小さい + んです = 小さいんです

    Unlike nouns and な-adjectives, い-adjectives can't take だ to form a sentence. For this reason, we don't need something like particle な to attach んです.

    ❌ 小さい

    ❌ 小さいんです

    Just like with nouns and な-adjectives, い-adjectives in the past tense or in negative form can take んです, too:

    • 小さかったんです。 (past)
    • It's that it was small.
    • 小さくないんです。 (negative)
    • It's that it isn't small.

    んです with Verbs

    Similarly to い-adjectives, verbs can connect directly to んです as well. Let's try it out with the verb, 書く (to write):

    書く + んです = 書くんです

    You can conjugate the verb into any form you wish, and then just stick んです on the end to add an explanatory note. Pretty useful, right?

    So, it works in the past tense:

    • 書いたんです。
    • It's that I wrote it.

    The negative:

    • 書かないんです。
    • It's that I will not write it.

    Or even something super advanced like the causative passive form (in this case, in the past tense too):

    • 書かせられたんです。
    • It's that I was made to write.

    Wait a second… です can only be used with nouns and adjectives, right? Why are we using it with verbs? It's all thanks to that single hiragana character, ん, that comes between the verb and です. ん (and its formal version, の) is a "nominalizer," which is a fancy way of saying it makes whatever comes before it function kind of like a noun. You'll also see the nominalizer の in sentences where a verb functions as the subject of a sentence. For example:

    • 食べるが僕の趣味です。
    • Eating is my hobby.

    Using んです for Explaining

    Now that we've gotten all the structural information out of the way, let's jump into how we can use んです. As we mentioned at the very beginning of this page, んです indicates that the speaker and listener share a context in which the statement was made. This creates a variety of different nuances, the most common of which is to add an explanatory tone to a statement.

    Imagine that you just found out your friend started studying Japanese with a tutor. You ask them what made them decide to start that up, and they reply:

    • 日本へ留学するんです。
    • (It's because) I will study abroad in Japan.

    The use of んです here adds an implied "it's because" to the statement, which is appropriate since your friend is explaining why he began studying with his tutor. In this case, 日本へ留学します by itself is not as suitable because it lacks that explanatory tone that んです adds. In other words, without んです, your friend's statement doesn't indicate that their statement is in response to your question, and it sounds kind of like a random declaration of their plan.

    Using んです to Ask for an Explanation

    On the flip side, you can also use んです to seek explanation in the form of a question. When doing this, particle か is often attached to the end of the sentence as a question marker.

    • なぜ泣いているんですか?
    • Why are you crying?

    Particle か is not obligatory to make this question, however. You can also omit it and use rising intonation to indicate you're seeking an explanation for this person's tears. However, adding か also makes your speech more natural.

    So let's say you asked this question to your friend, the one who wants to study abroad in Japan. It turns out that his girlfriend really didn't like the idea of him moving to another country. To answer your question, he uses んです because his statement is an explanation of why he is crying:

    • ⭕️ フラれたんです。
      ❌ フラれました。
    • I was dumped.

    Ouch, that sucks 😭! Remember, んです is used to acknowledge shared context between speaker and listener, and since you are both thinking about the question you asked, its more appropriate to respond with んです.

    In fact, there is a common phrase used to ask for further explanation when something is obviously wrong:

    • どうしたんですか?
    • What's wrong?

    Or, perhaps you've heard the more informal version of this:

    • どうしたの?
    • What's wrong?

    In either case, there needs to be some kind of shared context between you and the person you're asking (such as a sad look on their face), or else this might sound a bit odd.

    When Not to Use んです

    Speaking of when んです sounds strange, let's take a look at a few examples of these situations.

    Imagine you are walking with your friend, and you're getting hungry. If you want to know whether she's getting hungry too, what would you say? If you use んです, your friend is likely to get a puzzled look on her face:

    • お腹空いたんですか?
    • Are you hungry?

    This is a strange way to ask because んです indicates that there is a contextual reason for why you assumed that your friend is hungry. If she looked grumpy or her stomach was growling, then it would have made more sense to ask in this way.

    Another situation んです comes off as unnatural is when you're introducing yourself for the first time. By nature of the situation, you're talking to someone who doesn't know you, so there is no expectation of shared context or information. Because of this, んです is generally not suitable in self introductions.

    • ❌ 出身は札幌なんです。
      ⭕️ 出身は札幌です。
    • I'm from Sapporo.

    Of course, this is not a hard and fast rule; there may be some situations in which you might use んです. For example, if a new acquaintance asks you, "why aren't you wearing a jacket on a cold day like this?," you might respond saying 出身は札幌なんです. The point is, there has to be a shared contextual reason for answering in this way.