Die heruntergelassene Jalousie macht das Zimmer dunkel.

Jalousie is a feminine noun in German, so its basic article is die:

• die Jalousie = the blind
• eine Jalousie = a blind

In this sentence, die can mean either:

• the lowered blind, or
• just mark a specific feminine noun in context

The plural is usually die Jalousien.

heruntergelassene means lowered or let down.

It comes from the verb herunterlassen, which means to lower or to let down.

So:

• herunterlassen = to lower / let down
• heruntergelassen = lowered / let down
• die heruntergelassene Jalousie = the lowered blind

Here it works like a past participle used as an adjective before the noun.

It is built from the verb herunterlassen.

The parts are:

• herunter- = down
• lassen = to let / to have something done / to leave, depending on context

The past participle is:

• heruntergelassen

When that participle is placed before a noun like an adjective, it takes an adjective ending:

• die heruntergelassene Jalousie

So the -e at the end is not part of the participle itself; it is the adjective ending required by the grammar of the sentence.

Because it is an adjective-like word standing before the noun Jalousie, and it must agree with the noun.

Here we have:

• die = feminine singular nominative
• Jalousie = feminine singular
• so the adjective ending is -e

This is the same pattern as in:

• die offene Tür
• die geschlossene Tür
• die rote Lampe

So die heruntergelassene Jalousie follows the same rule.

Yes. In this sentence, machen works very much like English make in the sense of cause something to become a certain state.

Pattern:

• etwas macht etwas + Adjektiv

So:

• Die heruntergelassene Jalousie macht das Zimmer dunkel.
• literally: The lowered blind makes the room dark.
• more natural meaning: The lowered blind darkens the room or makes the room dark

This is a very common German structure, for example:

• Der Regen macht die Straße nass.
• Das Licht macht den Raum hell.

das Zimmer is in the accusative case because it is the direct object of macht.

The sentence structure is:

• Die heruntergelassene Jalousie = subject
• macht = verb
• das Zimmer = direct object
• dunkel = result/state caused

Since Zimmer is a neuter noun, the article is:

• nominative: das Zimmer
• accusative: das Zimmer

So it looks the same in both cases. That is why you do not see a visible change here.

Because dunkel is not directly describing the noun inside the noun phrase. It is a predicative adjective: it tells you the resulting state of das Zimmer after the action of machen.

Compare:

• das dunkle Zimmer = the dark room
  Here, dunkle is an attributive adjective before the noun, so it takes an ending.

• Die Jalousie macht das Zimmer dunkel.
  Here, dunkel comes after the object and describes the result, so it does not take an ending.

This is the same as:

• Das Wetter ist schön.
• Er macht die Tür auf.
• Sie färbt die Wand rot.

Predicative adjectives in German usually stay in the basic form.

It often translates as blind, but the exact English word depends on the type.

In everyday German, Jalousie usually refers to a window covering with slats or a blind-like covering. Depending on context, English might use:

• blind
• window blind
• sometimes shade
• sometimes shutter, though that can also be Rollladen or another term depending on the type

So Jalousie does not always match one single English word perfectly.

Yes, absolutely.

That sentence means:

• The blind is lowered / has been lowered

The difference is grammatical:

• die heruntergelassene Jalousie
  Here the participle comes before the noun and acts like an adjective.

• Die Jalousie ist heruntergelassen.
  Here heruntergelassen is used after the verb sein as part of the predicate.

Both are correct, but they are used in different sentence structures.

The basic order is:

• Die heruntergelassene Jalousie = subject
• macht = finite verb
• das Zimmer = object
• dunkel = result adjective

So the pattern is:

Subject + Verb + Object + Result adjective

This is normal German main-clause word order, where the conjugated verb is in second position:

• Die heruntergelassene Jalousie macht das Zimmer dunkel.

You could also move another element to the front for emphasis, but then the verb still stays in second position, for example:

• Das Zimmer macht die heruntergelassene Jalousie dunkel. — this changes the meaning and is wrong for the intended idea
• Dunkel macht die heruntergelassene Jalousie das Zimmer. — grammatically possible in a poetic or marked style, but very unusual

So the original sentence is the natural word order.

Yes, herunterlassen is a separable verb.

That means in a normal present-tense main clause, the prefix often moves to the end:

• Ich lasse die Jalousie herunter.

But in the infinitive or past participle, it stays together:

• die Jalousie herunterlassen
• die heruntergelassene Jalousie
• Ich habe die Jalousie heruntergelassen.

This is why learners often need to recognize that heruntergelassene is related to lässt ... herunter.