"Hol vannak azok a nagy folyók?"

Translation: Where are those large rivers?

[MarkMenges]

Why is it "azok A nagy..." instead of "azok nagy..."?

[jsiehler]

The demonstrative adjectives ez, az, ezek, azok (this, that, these, those) always require a definite article (a or az) right after them, before the noun (and before any other adjectives)

ez a busz - this bus

azok a kutyák - those dogs

az az orosz lány - that Russian girl

and so on.

[Maminti.]

But: Azok nagy kutyák - Those are big dogs
** Azok a kutyák nagyok - Those dogs are big

[Renardo_11]

Jsiehler's explanation is about that/those as demonstrative adjectives; s/he explicitly mentioned it. In your first example those is a pronoun.

[MarkMenges]

Thanks! For some reason it sounds funny in plural.

[jsiehler]

It will sound even funnier when you add in postpositions and say things like azok között a kutyák között which glosses as "those-between-the-dogs-between", and seems like a pretty baroque way to say "between those dogs" - but you get used to it. Pretty soon it'll sound normal and the wrong way will sound jarring.

[MarkMenges]

Wow. Can't wait to reach that level! ;D