"Kati can't hear."

Translation: Kati nem hall.

[SamanthaGasmire]

Why can it not be Kati nincs hall?

[Stuttgart3]

Nem means "no" or "not". Nincs means something doesn't exist or there isn't any of it. Also, you can think of it as nincs= "nem van" (nem van is NOT said in Hungarian).

[Teeeds]

Wouldn't "Kati nem hall" be better translated as "Kati doesn't hear"? I answered "Kati nem tud hallni", but this wasn't accepted.

[SamanthaGasmire]

To me this sounds like you are saying "Kati doesn't know how to hear" which implies a different meaning. Hope this helps