Bibliotekar će završiti razduženje tek kada korisnik vrati primerak.

Serbian commonly forms the future with:

• a present-tense form of hteti (ću, ćeš, će, ćemo, ćete, će)
• plus the infinitive

So:

• će završiti = will finish / will complete

Here, će is the 3rd person singular form, matching bibliotekar.

A few examples:

• Ja ću doći. = I will come.
• Ona će čekati. = She will wait.
• Bibliotekar će završiti... = The librarian will finish...

After time words like kada (when), Serbian often uses the present tense where English uses a future form.

So:

• kada korisnik vrati primerak literally looks like when the user returns the copy
• but in meaning it refers to the future: when the user has returned / when the user returns

This is very normal in Serbian.

Compare:

• Doći ću kada završim. = I will come when I finish.
• Pozvaću te kada stignem. = I’ll call you when I arrive.

So vrati is not a mistake or a present-time action here; it is the standard form in this kind of clause.

This is about aspect, which is very important in Serbian.

• vratiti = perfective, one completed return
• vraćati = imperfective, repeated/ongoing/habitual returning

In this sentence, the meaning is about a completed action: the user returns the copy, and only then can the process be finished. Because of that, Serbian uses the perfective verb:

• vrati

If you used vraća, it would suggest an ongoing or repeated action, which does not fit as well here.

Tek kada means something like:

• only when
• not until

It adds a sense of limitation: the first action cannot happen before the second one.

So:

• Bibliotekar će završiti razduženje tek kada korisnik vrati primerak.

means the librarian will finish the check-in/discharge process only when the user returns the copy.

Without tek, kada would simply mean when, and the sentence would sound less emphatic.

Razduženje is a noun. In this context, it refers to the act or process of clearing an item from someone’s responsibility, such as checking in a library item after it has been returned.

It comes from the verb family related to razdužiti / razduživati, which can mean to clear, discharge, or remove responsibility/accountability for something.

In library language, razduženje is more specific and administrative than a simple word like vraćanje (returning).

So here it is basically the formal process of recording that the borrowed copy has been returned.

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

But for many masculine inanimate singular nouns, the accusative looks exactly the same as the nominative.

So:

• nominative: primerak
• accusative: primerak

That is why it does not visibly change.

Compare:

• Korisnik vraća primerak. = The user returns the copy.
• Vidim sto. = I see the table.

But with a masculine animate noun, you would usually see a different accusative form:

• korisnik → korisnika in the accusative

Serbian does not have articles like English the and a/an.

So:

• bibliotekar can mean the librarian or a librarian
• korisnik can mean the user or a user
• primerak can mean the copy or a copy

The exact meaning depends on context.

In this sentence, English would probably use the librarian, the user, and the copy, but Serbian expresses that without articles.

Yes. Kad is a very common shorter form of kada.

So this would also be natural:

• Bibliotekar će završiti razduženje tek kad korisnik vrati primerak.

The meaning stays the same.

Very roughly:

• kada can sound a little more neutral or formal
• kad can sound a little more conversational

But both are standard and widely used.

No, Serbian word order is fairly flexible, although some orders sound more neutral than others.

The given sentence is natural and clear:

• Bibliotekar će završiti razduženje tek kada korisnik vrati primerak.

You could also hear variations such as:

• Tek kada korisnik vrati primerak, bibliotekar će završiti razduženje.

This puts more emphasis on the condition/time point.

However, the position of će follows clitic rules, so you cannot move words completely freely. Serbian word order is flexible, but not random.

Će is a clitic, and Serbian clitics tend to appear near the beginning of their clause, often in the so-called second position.

So:

• Bibliotekar će završiti... is normal
• Tek kada korisnik vrati primerak, bibliotekar će završiti... is also normal in the second clause

Clitics such as će, sam, si, je, ga, se often follow this placement pattern.

This is why Serbian learners often need to learn not just verb forms, but also where these short words naturally go.

Završiti is perfective. It means to finish / to complete as a completed whole.

That fits this sentence well because the librarian will complete the process at a specific point—after the copy is returned.

The imperfective partner is usually:

• završavati = to be finishing / to finish habitually or over time

So:

• će završiti = will finish completely
• će završavati would suggest an ongoing or repeated process, which is not the intended meaning here

Yes, the meaning overlaps with not until.

Because of tek kada, the sentence expresses that the librarian cannot complete the process before the return happens.

So these English versions are all close:

• The librarian will finish the check-in only when the user returns the copy.
• The librarian will not finish the check-in until the user returns the copy.

That not until sense is exactly the nuance that tek kada adds.