〜っこない
Could not possibly 〜っこない
Meaning
A blunt, casual denial — "there is no chance ~", "could not possibly ~".
Formation
[verb ます-stem] + っこない
Notes
Spoken only, and emphatic: そんなの分かりっこない. Same force as わけがない but far more colloquial, so it is out of place in writing or polite speech. Cannot attach to a noun.
Examples
そんな難（むずか）しい問題（もんだい）、分（わ）かりっこないよ。
A question that hard? No chance I could work it out.
Breakdown
一日（いちにち）で終（お）わりっこありません。
There is no chance of finishing in a day.
Breakdown
練習（れんしゅう）しなければ勝（か）てっこない。
Without practice there is no way we can win.
Breakdown
あの人（ひと）が来（く）るなんて、あり得（え）ないよ。信（しん）じられっこない。
Him coming? Impossible. I could never believe it.
Breakdown
こんなにたくさん、食（た）べられっこないよ。
This much? I could never eat it all.
Breakdown
⚠️ Often confused with
〜わけだ
That is why 〜わけだ
Draws a conclusion that follows naturally — "so that's why ~", "no wonder ~", "it works ou...
〜わけではない
It is not that 〜わけではない
A partial denial — "it is not that ~", "that does not mean ~". Softens rather than rejects...
〜わけがない
There is no way 〜わけがない
A flat denial of possibility — "there is no way ~", "it is impossible that ~".
〜に決まっている
Bound to be 〜に決まっている
Says an outcome is obvious — "of course ~", "it is bound to be ~".
〜とは限らない
Not necessarily 〜とは限らない
"Not necessarily ~", "it is not always the case that ~".
〜ものだ
One should / used to 〜ものだ
Three uses: a general truth, nostalgia for what one used to do, and mild moral advice.
〜に過ぎない
Merely 〜に過ぎない
"Merely ~", "no more than ~".
〜というものだ
That is what ~ is 〜というものだ
"That is what ~ really is" — the speaker's verdict stated as a general truth.
〜にほかならない
Nothing other than 〜にほかならない
"Is nothing other than ~", "is precisely ~".