"I do not know whether those windows are closed."

Translation: Nevím, jestli jsou ta okna zavřená.

[filigree2]

Is the use of neznám in this context incorrect? "Neznám jestli ta okna jsou zavřená."

[endless_sleeper]

It's incorrect.

[Kad759907]

"nevím, jsou-li ta okna zavřená" is an accepted answer.
Can anyone explain this 'jsou-li' to me? It looks totally unfamiliar...

[VladaFu]

It hasn't been taught yet, don't worry. "-li" is a conjunction with the meaning of "if" in the form of an enclitic.

[Kad759907]

ok, díky :)

[Avtokrat]

Why is wrong Já nevím, zda jsou tamty okna zavřená.

[endless_sleeper]

tamtA ^ 'Okno' is a neuter.

[cricketswool]

Why does 'jsou' come before 'ta okna'?

[VladaFu]

It is one of the possible orders. Often there are many orders. The salient bit is what is first and especially what is last, because the last bit tends to be the focus.

In between, when we have no clitics (to be met later), we are quite (not completely) free.

[cricketswool]

Ok. Let me ask another way, then. On my first attempt I tried to simply use the same word order as in English: "Nevím, jestli ta okna jsou zavřená." What, specifically, is wrong with this construction?