"I like cheese!"

Translation: Lubię ser!

[va-diim]

Why is ser not in accusative case?

[luless]

It is. In this case Acc=Nom.

[va-diim]

Yes, but why? I don't know the rule. When does the accusative case match the nominative? Isn't "ser" masculine?

[luless]

https://en.wikibooks.org/wiki/Polish/Masculine_noun_declension

Rules on top. Also links to feminine and neuter.

[va-diim]

Thank you. So ser is masculine-inanimate, correct? In Russian, "ja liubliu syr," it's the same, but I keep making mistakes in Polish declension, trying to use my knowledge of Russian, so I'm not confident about declension anymore.

[immery]

Yes in Polish all neuter an masculine inanimate nouns have accusative=nominative. Ser is masculine inanimate But many food related nouns are exceptions- animate when they should not be. (tomato)

Tak, w polskim rzeczowniki rodzaju nijakiego, i nieżywotne rodzaju męskiego- mają biernik=mianownikowi. Ser jest męski, nieżywotny. Ale wiele rzeczowników dotyczących jedzenia jest wyjątkami, są żywotne , choć nie powinny (pomidor)