that is the thing

That’s the thing is a phrase that we use to introduce an opinion which shows disagreement or some kind of counter - argument from what the other speak just said. You’re identifying some kind of issue or problem or reason why something can’t happen or be true

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معنی فارسی احتمالی: مسئله دقیقن همینه

یه چیزی هست، یه مسئله ای هست
that’s the issue; that’s the problem; that’s the point

Person A: "We should take your car when we go out tonight. "
Person B: "That's the thing - I can't find my keys!"