"I have nothing in my pocket."
Translation:Non ho niente in tasca.
So, the meaning is understood from a convention about how to understand double negatives, not from exact translation? Are exact translations also acceptable?
Nope, it's not a convention, rather it's the grammar rule (negative concord) :)
It's the same in most Romance languages:
Interesting, I am reading a book called "Essential Italian Grammar," but I have not come across this yet. I can't wait to learn more!
I see how it's implied, but would using "mia" here be outright wrong? Duolingo doesn't accept it.
It would be fine, provided you put the article (non ho niente nella mia tasca); it's unnecessary, but it could be used to stress the possessive.
The double-negation rule doesn't apply to Italian: when a sentence is negated many words are negated as well. "Ho qualcosa" -> "Non ho niente"; "Ne ho uno" -> "Non ne ho nessuno".
Thanks this is helpful, so can I essentially "ignore" non at the beginning of the sentance? (I know this is not really very good practise when learning a language). Or does it serve some more complicated purpose in more complex sentances?