How does emphasis work for this sentence? I am trying to get a solid understanding of how emphasis works in Hungarian. I am assuming that because the adjective goes before the imaginary verb "van" that we are emphasising the word clean (are the streets CLEAN), or it is the neutral word order. If it were at the end, we'd be asking if the STREETS were clean, right?
Last question: Why is the adjective conjugated if it goes before the noun it describes?
The adjective here is a predicative adjective, not an attributive one -- it's not part of a noun phrase like "the clean streets", which would cause it not to be inflected. (And would require it to be after the article.)
It's specifically attributive adjectives (that come before a noun and modify that noun or specify it) that are not inflected - not any adjective that happens to come in the sentence before a noun.
With "Az utcák tiszták", one could still emphasize "tiszták", this is because you can't really tell where "van" would be. Let's change this sentence to past: "Az utcák voltak tiszták" vs "Az utcák tiszták voltak". Still, I'd say "Tiszták az utcák" is more "neutral" or at least more common to think of, without any context. No particular topic, just the statement as it is.
LOL! No joke - years ago, I was trying to learn Hungarian with my dad, and all of a sudden, I shouted "A szálloda tiszta?" from an example in the book I was using. He, as a native speaker, was taken aback by that because it sounded weird to him (like a lot of what we students to around here). He told me "It should be 'Tiszta a szálloda?' as in 'Is the hotel clean?'" He started laughing. Well, I wasn't done because I told him: "Nem tiszta. Piskos". Even with my limited Hungarian, we couldn't stop laughing.
Lo and behold, that exchange became a long-running joke between us. "Tiszta a szálloda?" "Nem tiszta. Piskos."
This example brought back a funny memory :).