"What is this lesson about?"

Translation: O czym jest ta lekcja?

[MeganKunze1]

Which grammatical case would the answer to this question be?

[Jellei]

When "o" means "about" (so mostly), it takes Locative. Ta lekcja jest o poezji. (This lesson is about poetry).

[immerweiter]

czym o jest ta lekcja, is this possible?

[immery]

It is impossible. This is the most unbreakable rule of Polish word order.

it is always preposition+ (words describing noun/pronoun)+ noun/pronoun

Even poets don't break this rule.

[sdfbailey]

No, "o czym" is the only way round for this phrase. "O co" also exists, meaning "about what".

[Hereandthere715]

o co chodzi ta lekcja?

[alik1989]

You'll need w+locative. O co chodzi w tej lekcji?

[Glen624972]

Would "O czym to ta lekcja?" have been accepted?

[alik1989]

To only works with nouns on both sides.

[Glen624972]

OK, thank you