Pencere açık kalınca perde rüzgarda sallanıp duruyor.

It is made of three parts:

• açık = open
• kal- = stay, remain, be left
• -ınca = when, once, since, after

So açık kalınca means when it stays open, once it is left open, or since it remains open, depending on context.

With things like doors and windows, açık kalmak is very common Turkish for to remain open or to be left open.

Because açık kalmak is an idiomatic way to talk about a state continuing.

• açık olmak = to be open
• açık kalmak = to stay open, remain open, be left open

So pencere açık kalınca suggests not just the window is open, but the window stays open / has been left open. It highlights the continued state.

It can mean either, depending on context.

Common meanings of -ınca / -ince include:

• when
• once
• after
• sometimes since / because

In this sentence, both ideas fit:

• When the window stays open...
• Since the window is left open...

The Turkish form itself allows both, and the situation tells you which nuance is strongest.

Because pencere already acts as the subject.

In English, we often say when it stays open, but Turkish does not need an extra pronoun there. The noun pencere is enough:

• Pencere açık kalınca = when the window stays open

Turkish often leaves out pronouns when they are unnecessary.

Turkish has no articles like English a/an and the.

So:

• pencere can mean a window or the window
• perde can mean a curtain or the curtain

Context tells you which one is meant. In this sentence, English will usually use the because the meaning is specific and understood from the situation.

Because perde is the subject of the main clause, not the direct object.

• perde = the curtain
• perdeyi = the curtain as a definite direct object

Here, the curtain is the thing doing the action:

• perde ... sallanıp duruyor = the curtain keeps swaying

So it stays in the basic form perde.

rüzgarda means in the wind.

It is:

• rüzgar = wind
• -da = in, at, on

So:

• rüzgarda = in the wind

This is the locative case. It shows the setting or environment where the action happens.

Also, the suffix is -da rather than -ta because rüzgar ends in the voiced consonant r.

Yes.

• rüzgarda = in the wind
• rüzgardan = from the wind or because of the wind

In this sentence, rüzgarda paints the scene: the curtain is moving in the wind.
If you said rüzgardan, the cause would be more explicit: because of the wind.

Both can be possible in different sentences, but rüzgarda sounds very natural here.

It comes from sallanmak, which means to sway, swing, rock, dangle.

The ending -ıp / -ip / -up / -üp is a converb ending. It often links one verb to another and can mean things like:

• and ...
• by ...-ing
• ... and then ...

So sallanıp duruyor is literally something like it sways and stays or it sways and keeps on. In natural English, that becomes it keeps swaying or it keeps flapping.

Because durmak is being used as an auxiliary here.

By itself:

• durmak = to stand, stay, stop

But after another verb, it can add the idea of a repeated, continuing, ongoing action.

So:

• sallanıyor = it is swaying
• sallanıp duruyor = it keeps swaying, it just goes on swaying

This structure often makes the action feel more vivid, more continuous, and sometimes slightly emphatic.

sallanıyor is simpler and more neutral: it is swaying.

sallanıp duruyor adds extra aspect:

• the movement keeps continuing
• it may be repetitive
• it feels more descriptive or vivid

So the difference is roughly:

• Perde sallanıyor. = The curtain is swaying.
• Perde sallanıp duruyor. = The curtain keeps swaying / won’t stop swaying.

That is why the original sentence feels more expressive than a plain progressive form.