Grammar Info
N3 Lesson 5: 6/21

訳(わけ)がない
there is no way, there is no reason, it is impossible, cannot be

Structure
Casual
Polite
Verb[る](1) + わけない
[な]Adjective + + わけない
[い]Adjective + わけない

(1) Verb[た]
Verb[る](1) + わけありません
[な]Adjective + + わけありません
[い]Adjective + わけありません

(1) Verb[た]
Details
Register Standard
使用域 一般
Information
One of the strongest ways to use the 名詞(めいし) わけ in Japanese, is in the expression わけがない. This is regularly translated as ‘there is no way that (A)’, or ‘it is impossible that (A)’. However, as mentioned in other わけ lessons, わけ is used very similarly to ‘so’ in English, so may also be thought of as ‘it is SO not (A)’, with ‘so’ being used for emphasis. In this structure, わけ is combined with the 格助詞(かくじょし) (case marking particle) が, and the い-Adjective ない.
わけがない may be used with verbs, or adjectives in their 連体形(れんたいけい) (attributive form).
  • このステーキ2キロもある?!こんな一人(ひとり)食(た)べれるわけがない
    This steak weighs 2kg?! I SO can’t eat something like this alone!
  • キムラシェフ作(つ)ったパスタよ、不味(まず)い訳(わけ)がないじゃん!
    This pasta is made by Chef Kimura, there is no way this would taste bad!
  • このアパートは線路(どうろ)隣(となり)あるから静(しず)かなわけがない
    This apartment is next to the train track, so there is no way it is quiet.
Caution
Compared to わけではない, わけがない is much stronger, and emphasizes the ‘non-existence’ of something. This can be thought of as similar to the difference between ‘it is so that it isn’t (A)’ (for わけではない), and ‘it is SO not (A)’ (for わけがない).
  • 彼(かれ)はいつも遊(あそ)んでいる、暇(ひま)なわけではない
    He is always going out, but it is not necessarily so that he has a lot of free time.
  • 彼(かれ)はいつも仕事(しごと)ているから、暇(ひま)なわけがない
    Since he is always working, he SO does not have any free time.
‘It is so that it isn’t (A)’ highlights that (A) is a thing that exists, but not in the way of (A). On the other hand, ‘it is SO not (A)’ highlights that no part of (A) whatsoever can be considered to be correct/accurate.
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日本人(にほんじん)ならそんなことを言(い)うわけがない
There is no way that a Japanese person would say that.
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手(て)を繋(つな)いでいるので、子供(こども)は勝手(かって)にどこかに行(い)くわけがない
I am holding my kid's hand, so there is no way that he would just run off somewhere.
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日本(にほん)にいるだけで、日本語(にほんご)を学(まな)べるわけがない
There is no way you can learn Japanese from just being in Japan.
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Books
Tae Kim's Japanese Grammar Guide
Page 285