Az ablak be van csukva, mert hűvös a levegő.

Hungarian has two forms of the definite article:

• a before a consonant
• az before a vowel

Since ablak begins with the vowel a, it must be az ablak.

Examples:

• a ház = the house
• az ajtó = the door
• az ablak = the window

This is a very common Hungarian structure meaning that something is in a closed state.

It consists of:

• be = a verbal prefix, here suggesting shut/closed
• van = is
• csukva = a -va/-ve participle from csukni = to shut, to close

So be van csukva means something like is shut or is closed.

A very literal breakdown would be: the window in-is shut, but natural English is simply the window is closed.

Not exactly.

English often says the window is closed, and that can be either:

• a passive of an action, or
• a description of a state

In Hungarian, be van csukva is mainly a state/result expression: the window is in the state of having been shut.

It usually does not focus on who did the action.

If you want to say that someone actually closed it, Hungarian more naturally uses an active sentence, for example:

• Valaki becsukta az ablakot. = Someone closed the window.
• Becsukták az ablakot. = They / people closed the window.

Because Hungarian verbal prefixes often separate when another finite verb stands in the structure.

The basic verb is becsukni = to close, to shut.

But in this sentence, the finite verb is van, so the prefix appears before van:

• be van csukva

This is normal Hungarian word formation and word order.

So learners should think of be van csukva as the usual form of this expression, not as something strange or irregular.

Because Hungarian usually leaves out van in the present tense, third person when the predicate is a noun or adjective.

So:

• A levegő hűvös. = The air is cool.
• not A levegő van hűvös.

This is a basic rule of Hungarian.

But in the past or future, the verb appears again:

• A levegő hűvös volt. = The air was cool.
• A levegő hűvös lesz. = The air will be cool.

Both are possible.

• Hűvös a levegő
• A levegő hűvös

The difference is mainly about information structure and emphasis.

Hűvös a levegő is very natural when the important new information is hűvös = cool/chilly.

A levegő hűvös sounds a bit more topic-first, as if you are specifically talking about the air.

Hungarian word order is much more flexible than English word order, and it often reflects what is already known versus what is being highlighted.

Hungarian uses the definite article more often than English.

In a levegő, the speaker means the air in the relevant situation: the air here, outside, in the room, around us, and so on.

So hűvös a levegő is naturally the air is cool in Hungarian, even if English might sometimes say just air is cool in a different kind of sentence.

Also, without the article, the structure would usually change:

• hűvös levegő = cool air

That is a noun phrase, not a full sentence.

Mert means because. It introduces the reason.

So the sentence structure is:

• Az ablak be van csukva = The window is closed
• mert hűvös a levegő = because the air is cool

Together: the second part explains why the window is closed.

You can also put the mert clause first:

• Mert hűvös a levegő, az ablak be van csukva.

But the original order is more neutral and more common in everyday use.

Yes, that is also possible.

• Az ablak csukva van.
• Az ablak be van csukva.

Both can mean the window is closed.

The version with be keeps the sense of being shut closed, and it is very common with things like doors and windows.

The version without be is also understandable and natural, but be van csukva often sounds a bit more idiomatic for something that has been shut.

Csukva is a -va/-ve participle formed from the verb csukni.

This form often describes a resulting state:

• írva = written
• nyitva = open
• zárva = closed
• csukva = shut/closed

In be van csukva, csukva is not acting like a normal finite verb. It is part of the expression describing the state of the window.

This is why the sentence uses van together with it.