Japanese Grammar

Explanation & Emphasis: 〜んです / 〜のです

The grammar ~n desu / ~no desu is incredibly common in spoken Japanese, but hard to translate directly. It signals that you are providing an EXPLANATION or seeking one.

What does ~n desu mean?

Think of ~n desu as adding the nuance: 'The fact is that...' or 'The reason is that...' or simply 'You see,...'. It signals to the listener that what follows is relevant context or an explanation.

GIVING an explanation: 'Sushi o tabemasen.' (I don't eat sushi) is a plain fact. 'Sushi o taberarenain desu.' (The fact is I can't eat sushi) — implies there's a reason, like an allergy.

SEEKING an explanation: 'Dou shitan desu ka?' means 'What happened / What's the matter?' (Asking for an explanation of an unusual situation).

How to form ~n desu

Verbs and I-Adjectives
Rule
Plain Form + んです / のです
Just add 'n desu' or 'no desu' to the plain form
行く (iku)
行くんです (iku n desu)
The fact is (I) am going / (I) go because...
高い (takai)
高いんです (takai n desu)
The thing is, it's expensive...
Na-Adjectives and Nouns
IMPORTANT: Drop だ, add なんです
な + んです
Na-adj/noun: add 'na' BEFORE n desu
元気だ (genki da)
元気なんです (genki na n desu)
The thing is, (I) am well...
学生だ (gakusei da)
学生なんです (gakusei na n desu)
The fact is, (I) am a student...
Casual Speech
In casual speech
Plain Form + んだ (n da)
Replace 'desu' with 'da' for casual
行くんだ (iku n da)
行くんだ!
Oh, so you're going! (Realization)
Question: 行くの?
Iku no?
Are you going? (Seeking explanation/confirmation)

Example Sentences

熱があるんです。だから、今日は休みます。
Netsu ga aru n desu. Dakara, kyou wa yasumimasu.
The thing is, I have a fever. That's why I'm taking today off. (Explanation)
どうしたんですか?
Dou shita n desu ka?
What's the matter? / What happened? (Seeking explanation)
これ、高いんだよ!
Kore, takai n da yo!
This is expensive, you know! (Emphasizing a fact)

Teacher's Advice

Overusing ~n desu

~n desu makes everything sound like you are explaining yourself, which can feel like over-justifying in some contexts. For simple factual statements with no implied explanation, just use the plain masu/desu form. Use ~n desu when there is an emotional or contextual reason behind what you are saying.

JLPT Exam Patterns

  • Na-adjectives and nouns use 'na' before n desu: 元気『な』んです (N4)
  • Using ~n desu ka to ask for an explanation in conversation (N4)
  • ~n da is the casual equivalent for dialogue questions in the N4 reading section

Sound More Natural

Practice adding ~n desu to sentences to make explanations feel natural.

Start Practice →