Questions & Answers about Młody student nie ma telewizora.
Why is the word for TV here telewizora instead of just telewizor?
Because of the word nie. The verb ma (has) normally takes the Accusative case for its object. But in Polish, whenever a verb like this is negated with nie, the object of the sentence flips to the Genitive case. So, the basic word telewizor changes to telewizora.
I learned that masculine non-living nouns usually take -u in the Genitive. Why does telewizora end in -a?
You are right that many masculine inanimate (non-living) nouns take an -u ending in the Genitive case. However, there are exceptions that take -a instead. A very common rule of thumb is that electronic devices and everyday tools usually take the -a ending. This is why we say telewizora, and similarly smartfona (smartphone) or laptopa (laptop).
Why doesn't the negative word nie change the case of the subject młody student?
The Genitive of negation rule only affects the direct object (the thing that is not being had, seen, or done). It never affects the subject of the sentence. Because the young student is the one doing the action, młody student stays in the basic Nominative case.
Why does the adjective młody end in -y?