Grammar Info
N5 Lesson 3: 12/13

んだ・んです
Explanatory, Emphasis, The fact is

Structure
Casual
Formal
Verb + (1) +
[い]Adjective + (1) +
[な]Adjective + + (1) +
Noun + + (1) +

(1)
Verb + (1) + です
[い]Adjective + (1) + です
[な]Adjective + + (1) + です
Noun + + (1) + です

(1)
Details
Part of Speech Expression
Word Type Auxiliary Verb
Register Standard
品詞 表現
単語の種類 助動詞
使用域 一般
Information
のです is a construction with several different forms, each meaning roughly the same thing. This expression behaves similarly to and です by themselves (asserting that something is true). However, the addition of の strengthens the relationship being highlighted. Due to this, it will come across a bit like ‘it is a fact that (A)’ in English.
  • ここコーヒー美味(おい)しんです
    The coffee here is really good. (Strong assertion)
  • 私(わたし)悪(わる)のです
    I am the one to blame. (Strong assertion)
In these sentences, we can think of the , or as simply adding emphasis to the statement. Due to adding emphasis, this expression will be heard very frequently in explanations.
Caution
There is no real difference between and . Only is considered ‘correct Japanese’, but evolved to make things easier to say. is the most common form in spoken Japanese, and the use of could be considered a bit formal, or ‘stiff’.
While both the and です forms are equally as natural, only the です form will be used if adding to the end ~んです. This construction shows that the speaker is looking for an explanation about something.
  • あなたこれ欲(ほ)しんです
    Is this what you want?
  • お腹(なか)空(す)いたのです
    Have you become hungry? (Are you hungry?)
Slow Male
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Hide Japanese
Hide English
いいんです
Is it good?
[asking for explanation・explaining・emphasis]
Play  
赤(あか)いいんです
Is red good?
[asking for explanation・explaining・emphasis]
Play  
いいのです
Is it good?
[asking for explanation・explaining・emphasis]
Play  
Books
Genki I
Page 230
Genki I 2nd Edition
Page 270
[DBJG] A Dictionary of Basic Japanese Grammar
Page 325
みんなの日本語 II
Page 12 [CH 26]
Marugoto Elementary 1 (A2) Rikai
Page 154
[DBJG] A Dictionary of Basic Japanese Grammar
Page 322
Tae Kim's Japanese Grammar Guide
Page 73