Questions & Answers about Stary aktor nie pisze artykułu.
Why is the word for 'article' artykułu instead of artykuł?
This is the Genitive of negation in action! The verb pisać (to write) normally takes a direct object in the Accusative case. But when you add nie to negate the sentence, that direct object must change to the Genitive case. Since artykuł is the thing not being written, it becomes artykułu.
Why does the Genitive form of artykuł end in -u and not -a?
For masculine inanimate nouns in the Genitive case, the ending is usually either -u or -a. There is no perfect rule for which one to use, but many imported words (loanwords) and abstract concepts take the -u ending. Artykuł belongs to this group!
If the sentence is negated, why doesn't stary aktor change to the Genitive case too?
The Genitive of negation only affects the direct object of the verb, which is the thing receiving the action (in this case, the article). The subject doing the action (the old actor) always stays in the Nominative case, regardless of whether the sentence is positive or negative.
Can nie pisze also mean 'does not write'?
Yes! Polish present tense covers both the English simple present ('does not write') and present continuous ('is not writing'). You can tell which one is meant from the context.