Ako ne budeš kod kuće, poštarka može da donese paket sutra.

After ako when you are talking about a future situation, Serbian often uses the budem / budeš / bude... forms, not the ordinary present sam / si / je... and usually not ćeš biti.

So:

• Ako nisi kod kuće = if you are not at home (now / generally)
• Ako ne budeš kod kuće = if you are not at home (at that future time)

This is a very common pattern in Serbian after words like ako, kad, čim, and similar conjunctions.

Yes, kod kuće is the normal fixed expression for at home.

There is a difference:

• kod kuće = at home
• u kući = in the house

So u kući focuses more on being physically inside the building, while kod kuće means being at home in the everyday sense. In this sentence, kod kuće is the natural choice.

Kod often means at someone's place / by / near. In kod kuće, it forms a set phrase meaning at home.

You will also see it in examples like:

• kod lekara = at the doctor's
• kod bake = at grandma's place
• kod mene = at my place

So here it is not being translated word-for-word; it is part of the usual Serbian way to say at home.

Poštarka is the feminine form, meaning a female postal worker or mail carrier. Poštar is the masculine form.

Serbian often makes profession nouns agree with the person's gender:

• poštar = male mail carrier
• poštarka = female mail carrier

So the sentence specifically refers to a woman.

In Serbian, after modal verbs like moći, it is very common to use da + present tense:

• može da donese

This is the most natural pattern in standard Serbian. An infinitive can sometimes appear in related contexts, but da + present is the form learners should expect most often in Serbian.

So može da donese is a very normal structure meaning can / may bring.

Because donese is from the perfective verb, and it fits a single completed action: bringing one package on one occasion.

• donese = bring once, successfully deliver
• donosi = brings / is bringing / brings habitually

In this sentence, the idea is one possible delivery event tomorrow, so the perfective donese is the natural choice.

Paket is the direct object, so it is in the accusative case.

But paket is a masculine inanimate noun, and for masculine inanimate nouns, the accusative singular is usually the same as the nominative singular. So:

• nominative: paket
• accusative: paket

That is why the form does not change.

In Serbian, ne is usually written as a separate word before the verb:

• ne znam
• ne mogu
• ne budeš

A few negative forms are written together, such as:

• nemam
• nisam
• neću

But with budeš, the normal spelling is ne budeš.

Yes. Serbian word order is fairly flexible, and sutra can move depending on emphasis.

For example, all of these are possible:

• Ako ne budeš kod kuće, poštarka može da donese paket sutra.
• Ako ne budeš kod kuće, poštarka može sutra da donese paket.
• Ako ne budeš kod kuće, sutra poštarka može da donese paket.

The version with sutra at the end is completely natural. Putting it elsewhere can shift the focus slightly, but the core meaning stays the same.

It can suggest either possibility or permission-like possibility, depending on context, but here it most naturally means it is possible that the mail carrier will bring the package tomorrow.

So it is less about the mail carrier's physical ability and more about what may happen. In everyday translation, can and may are both possible, but the real idea is possible future delivery.

Because Serbian has no articles. There is no direct equivalent of English a or the.

So paket can mean:

• a package
• the package

The exact meaning depends on context. Serbian speakers understand definiteness from the situation, word order, and previous conversation rather than from articles.