Questions & Answers about Ten nowy produkt nie ma żadnej wady.
Why is it żadnej instead of żaden or żadna?
Żadnej is the Genitive feminine singular form of żaden (none/not any). It is feminine to match the noun wada (flaw). It takes the Genitive case because the verb ma (has) is negated by nie. In Polish, whenever a direct object is negated, it switches from the Accusative case to the Genitive case.
The literal translation seems to be it does not have no flaw. Is this double negative required?
Yes, Polish strictly requires double negation. When you use a negative determiner like żaden, you must also negate the verb with nie. Saying the sentence without nie would be grammatically incorrect.
The English translation says flaws in the plural. Why is wady in the singular?
In Polish, żaden is almost always used with singular nouns, even when English uses the plural. Nie ma żadnej wady translates literally to does not have not a single flaw, which is the most natural way to express having no flaws in Polish.
Why does Ten nowy produkt stay in the Nominative case if the sentence is negative?
Negating a verb only affects the case of the direct object, which is the thing being acted upon or possessed (the flaw). The subject of the sentence (the product) is the one doing the action, so it always remains in the basic Nominative case as Ten nowy produkt.