訳がない & 訳じゃない may seem similar, but they have completely different meanings.
I would probably translate 訳がない as "There's no way." and 訳じゃない as "It is not the case." ない is the negative form of the verb ある, whereas じゃない or ではない is the negative copula. ない means "exist not" and じゃない means "is not". Although a lot of slang drops particles, you should really think of じゃない or ではない as a word on it's own.
Now here are some examples to illustrate the difference between 訳がない & 訳じゃない.
中国語が読めるわけがない。
There's no way I can read Chinese.
(Literally: "Chinese read can conclusion exists not." or "The conclusion that I can read Chinese exists not.")
中国語が読めないわけじゃない…
It's not the case that I can't read Chinese...
(Literally: "Chinese read can not conclusion is not..." or "It is not the conclusion that I can't read Chinese...")
Does that makes sense? 訳がない means "The conclusion doesn't exist" and 訳じゃない means "It is not the conclusion.". So 訳がない is used when you want to say "there is no way it is that conclusion" and 訳じゃない is used when you want to say "It is not that conclusion...(It is another conclusion)".
中国語が読めないわけじゃないよ… とても難しいんだよ！
It's not that I can't read Chinese, it's that Chinese is very difficult.
Difference between 訳がない &
Difference between 訳がない & 訳じゃない
訳がない & 訳じゃない may seem similar, but they have completely different meanings.
I would probably translate 訳がない as "There's no way." and 訳じゃない as "It is not the case." ない is the negative form of the verb ある, whereas じゃない or ではない is the negative copula. ない means "exist not" and じゃない means "is not". Although a lot of slang drops particles, you should really think of じゃない or ではない as a word on it's own.
Now here are some examples to illustrate the difference between 訳がない & 訳じゃない.
中国語が読めるわけがない。
There's no way I can read Chinese.
(Literally: "Chinese read can conclusion exists not." or "The conclusion that I can read Chinese exists not.")
中国語が読めないわけじゃない…
It's not the case that I can't read Chinese...
(Literally: "Chinese read can not conclusion is not..." or "It is not the conclusion that I can't read Chinese...")
Does that makes sense? 訳がない means "The conclusion doesn't exist" and 訳じゃない means "It is not the conclusion.". So 訳がない is used when you want to say "there is no way it is that conclusion" and 訳じゃない is used when you want to say "It is not that conclusion...(It is another conclusion)".
中国語が読めないわけじゃないよ… とても難しいんだよ！
It's not that I can't read Chinese, it's that Chinese is very difficult.