"I have nothing in the kitchen."
Translation:Non ho niente in cucina.
Since double negatives in English are positive, I said "io ho niente in la cucina" ...how would be interpreted in Italian?
That's not a valid sentence in Italian; you can avoid the double negative only if you put "niente" before the verb, as "niente ho in cucina", or in an interrogation, as "hai niente in cucina?", but the first word order is very rare (mostly poetry and a couple of dialects). "In la" is wrong as well, it's either "in" or "nella".
Nulla is usually a perfect synonym for niente; nullo is mostly an adjective meaning "equal to zero" in math or "void" in legal jargon (other meanings are archaic).
P.S. Back then I forgot to mention that "hai niente...?" doesn't mean "do you have nothing?" but "do you have anything?", so it's basically equivalent to "hai qualcosa...?"
nella is just in + la.
I have nothing in the kitchen. -> Non ho niente nella cucina. I have nothing in kitchen -> Non ho niente in cucina.
In this sentece you can use both, it does not make a big difference.
In Italian two negations don't cancel each other: instead, you negate each and every element of the sentence that can be negated (except adjectives I guess).
"In la" is inammissible in Italian, the contraction into "nella" is mandatory.
The one was in italian and I wrote it in english like "I have nothing in kitchen" and they assumed it wrong