Djed je prekrio djecu poplunom jer je prozor ostao otvoren.

Djed is in the nominative singular because it is the subject of the sentence—the person doing the action.

• djed = grandfather (nominative)
• djeda would be a different case, often genitive or accusative, depending on context

Here, Djed je prekrio... means Grandfather covered..., so the subject must be in the nominative.

This is the past tense in Croatian, formed with:

• the auxiliary verb je = is/has as a helper
• the past participle prekrio = covered

So:

• je prekrio = covered / has covered

This is the normal way to make the past tense in Croatian.

The participle prekrio agrees with the subject:

• djed is masculine singular
• so the participle is prekrio

If the subject were feminine, you would get prekrila; if plural masculine, prekrili, and so on.

Because djecu is the accusative case, used for the direct object—the people being covered.

• djeca = children (nominative)
• djecu = children (accusative)

So:

• Djeca su došla. = The children came.
• Djed je prekrio djecu. = Grandfather covered the children.

A learner often notices that djeca behaves a bit irregularly. It is a collective noun in form, and its cases do not pattern exactly like a simple regular plural noun, so it is worth memorizing:

• nominative: djeca
• genitive: djece
• dative: djeci
• accusative: djecu
• locative: djeci
• instrumental: djecom

Poplunom is the instrumental singular of poplun (duvet / quilt / blanket, depending on translation).

It is used here because Croatian often puts the thing used to cover someone in the instrumental after prekriti:

• prekriti nekoga nečim = to cover someone with something

So:

• djecu = the thing/person being covered
• poplunom = what they are covered with

This is a very common pattern:

• prekrio je stolnjakom stol = he covered the table with a tablecloth
• prekrila je dijete dekicom = she covered the child with a little blanket

Usually, no—not in this meaning.

• poplunom on its own is the normal instrumental meaning with a duvet/as the covering thing
• s poplunom usually means with the duvet in the sense of together with it

So:

• prekrio djecu poplunom = covered the children with a duvet
• bio je s poplunom = he was with the duvet / he had the duvet with him

After prekriti, the form without s is the natural choice for the material or object used to cover something.

Both are possible in some contexts, but they mean slightly different things.

• ostao otvoren = remained open / was left open
• bio otvoren = was open

In this sentence, ostao otvoren suggests that the window was still open, or that it had been opened earlier and was not closed afterward. That fits the context very well.

So the nuance is:

• bio otvoren = simple state
• ostao otvoren = state that continued or remained

Because otvoren is agreeing with prozor.

• prozor is masculine singular nominative
• after ostao, the adjective describing the subject also stays in the nominative:
  • prozor je ostao otvoren

This works like:

• Vrata su ostala otvorena. = The door/doors remained open.
• Dijete je ostalo mirno. = The child remained calm.

So otvoren is a predicate adjective matching the subject prozor.

Because there are two clauses, and each clause has its own verb phrase in the past tense:

1. Djed je prekrio djecu poplunom
2. jer je prozor ostao otvoren

Each clause needs its own auxiliary je.

So this is perfectly normal:

• je prekrio
• je ostao

Even though English might not always make this feel as noticeable, Croatian does.

Jer means because. It introduces a clause giving the reason.

So the structure is:

• main clause: Djed je prekrio djecu poplunom
• reason clause: jer je prozor ostao otvoren

Other Croatian words can also connect clauses, but jer is the standard straightforward word for because in sentences like this.

Yes, prekrio comes from the perfective verb prekriti.

That matters because perfective verbs usually present an action as completed, whole, or finished.

So prekrio djecu poplunom suggests a completed act: he covered them.

The imperfective counterpart would be something like pokrivati / prekrivati in contexts where you want to stress an ongoing, repeated, or habitual action.

Here, the perfective form is natural because this is a single completed action in the past.

Yes, Croatian word order is fairly flexible, but not completely free.

This sentence could be rearranged for emphasis, for example:

• Djed je djecu prekrio poplunom.
• Djecu je djed prekrio poplunom.

These all mean basically the same thing, but the focus changes slightly.

One important rule is that je, as a clitic, usually goes in second position in its clause:

• Djed je prekrio...
• jer je prozor ostao...

So while you can move larger elements around, the clitic placement still follows its own rules.

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

So:

• djed can mean grandfather or the grandfather
• prozor can mean a window or the window

The exact meaning is understood from context.

That is why the sentence can simply say:

• Djed je prekrio djecu poplunom...

without needing an article before the nouns.

No. Djed is the standard word, but learners may also hear other forms depending on region, family usage, or style, such as deda.

In standard Croatian, djed is the safest choice and the one used in this sentence.

So for a learner, it is best to treat:

• djed = standard Croatian form

Prozor is in the nominative singular because it is the subject of the clause jer je prozor ostao otvoren.

That clause means the window is the thing that remained open, so it must be in the nominative.

Compare:

• Prozor je otvoren. = The window is open.
• Otvorio je prozor. = He opened the window.

In the second sentence, prozor is the object, but because it is inanimate masculine singular, nominative and accusative look the same. In your sentence, though, its role is clearly that of the subject.

Croatian shows sentence roles largely through case endings and verb structure.

In this sentence:

• Djed = nominative subject of the first clause
• djecu = accusative direct object of prekrio
• poplunom = instrumental, the thing used for covering
• prozor = nominative subject of the second clause

Also, the verb meanings help:

• prekriti nekoga nečim naturally takes an object in the accusative
• ostati otvoren naturally describes the subject that remained open

So even though English learners often rely heavily on word order, Croatian gives you a lot of information through the forms themselves.