Absolutely convinced this is the first time this has ever been introduced. How are you supposed to know?!
I'm afraid that va-diim simplified too much. Negation doesn't automatically take Genitive.
Only Accusative, when negated, turns into Genitive. Accusative is the most common case, so people see a lot of "Genitive used in negations", but that's not exactly the truth. Every other case stays unchanged. Only Accusative changes.
My apologies for over-simplifying. So nouns in accusative case take the genitive case in negation. I had to write it again, for myself, to remember next time. Thank you, @Jellei
My mistake, there was a typo in my sentence. However, thanks for the quick response and clarifying that both are correct.
Is koszul plural here? What is the singular for shirt in this case? Maybe I'm assuming shorter words represent singular forms?
Nominative forms are: koszula (one shirt), koszule (plural shirts).
Here you have Genitive. Genitive is: koszuli (one shirt) and koszul (plural shirts).
"Koszula" = shirt (nominative) "Koszuly" = shirts (nom plural) "Koszulę" = shirt (accusative sin) "Koszuly" = shirts (acc plural) "Koszuly" = shirt (genitive singular) "Koszul" = shirts (genitive plural)
Am I correct?
It seems wrong to have this exercise here. The genitive hasn't been introduced at this stage, so it doesn't seem to make sense to have an exercise that uses the genitive.