"Ez az épület az Országház."

Translation: This building is the Parliament.

[Arcaeca]

"Parliament" here meaning the building itself (that's my guess) or the actual legislative body?

BTW, I'm jealous of you Hungarians' Parliament building. It dwarfs our puny Capitol Building :(

[Shamarth]

The legislative body is called parlament.

Országház refers to the building itself, but it's often also called Parlament.

[guirita123]

Ország = country
Ház = house
It's the building. . .and it's magnificent, complete with the crown jewels. :)

[StevenMans2]

Important difference here:

"Parliament" with no article in English is the building. "The Parliament" is the legislative body. As such"

This building is Parliament. (Or the Parliament building).

[DavidCarver]

"Parliament House" is the accepted term in several countries for the building where the Parliament meets - rejected by Duo, but might be appropriate here.

[Melissa_I-B]

Is there any reason why "This is the parliament building" should be market incorrect?

[RyagonIV]

Your grammar is a bit backwards. You're asking what "this" is, but the original sentence is asking what "this building" is.

[guntunge]

This is THE building, the parliament.
The building to rule them all... grammar wise there seems to be no indication were the invisible van has to appear in English.

Bonus questions: were lies the focus in such verbless sentences? And how would I move it?

[RyagonIV]

Punctuation is important here:

• This building is the Parliament. - Ez az épület az Országház.
• This is the building, the Parliament. - Ez az épület, az Országház.

Maybe more obvious:

• Téged akar meglátogatni, Kati. - He wants to visit you, Kati.
• Téged akar meglátogatni Kati. - Kati wants to visit you.

In a verbless sentence, the focus is only weak and if you're speaking the sentence, you can place the focus wherever you like by giving the important part some emphasis, for example:

• Ez az épület az Országház.
• Ez az épület az Országház.

In written text you'll have to rely on the power of context. Or on making it bluntly obvious:

• Ez az épület az Országház, nem a Vár.

[guntunge]

Was partly a thought if it is ambigious in speech.

Punctuation is unfortunately not at all checked in input and I have to admit that I barely pay attention to it.

So while I thought it should work that way in English I have pretty much zero knowledge about commas in Hungarian. Only exception were I occasionally wonder if that is proper ", és" (especially when English is translated to ", and" as well)

[RyagonIV]

Comma rules are pretty straightforward in Hungarian. It's mostly the same as in German: different clauses are separated by a comma, and the items in a list of three or more are separated by commas, except in front of és and vagy.

English does it somewhat differently. When you have different clauses that are separated by a conjunction, you usually don't add a comma:

• When we get back, I will buy you an ice cream. (Secondary clause in the front, so the conjunction "when" is not helping separating the clauses.)
• I will buy you an ice cream when we get back. (Secondary clause after main clause, so the conjunction is separarting the clauses. No comma necessary.)

In Hungarian you place a comma in both cases:

• Amikor visszajövünk, egy fagylalatot veszek neked.
• Egy fagylaltot veszek neked, amikor visszajövünk.

If you list three or more things in English, you usually put a comma in front of the "and" or "or". This is commonly referred to as "Oxford comma":

• I wanted to buy bread, milk, and butter.
• Are you dumb, blind, or do you just have no heart?

In Hungarian, there is usually no comma before és or vagy:

• Kenyeret, tejet és vajat akartam venni.
• Hülye vagy, vak vagy csak szívtelen?