Korisnik može da pozajmi publikaciju tek kada se učlani.

Both are possible in Serbian.

• može da pozajmi
• može pozajmiti

In standard Serbian, after verbs like moći (can, be able to), you can often use either:

• da + present tense
• the infinitive

The da + present structure is very common and natural in everyday Serbian.

So:

• Korisnik može da pozajmi publikaciju
• Korisnik može pozajmiti publikaciju

both mean essentially the same thing.

Pozajmi here comes from the perfective verb pozajmiti, while pozajmljuje comes from the imperfective verb pozajmljivati / pozajmljue? More commonly, learners meet the pair as:

• pozajmiti = to borrow/lend once, as a completed action
• pozajmljivati = to borrow/lend repeatedly, habitually, or as an ongoing process

In this sentence, the point is about whether the user is allowed to complete the act of borrowing an item, so the perfective verb fits well.

After može da, Serbian often uses a perfective present form to express a single possible action:

• može da pozajmi = can borrow

This does not mean present time in the English sense. It means the action is possible as a whole.

Publikaciju is in the accusative singular.

The dictionary form is:

• publikacija = publication

Because it is the direct object of the verb pozajmi (borrow), it goes into the accusative:

• publikacija → nominative
• publikaciju → accusative

This is a regular pattern for many feminine nouns ending in -a:

• knjiga → knjigu
• novina → novinu
• publikacija → publikaciju

Grammatically, yes, publikacija literally means publication.

But in library or administrative contexts, it can refer more broadly to a library item or published material, such as:

• a book
• a journal
• a magazine
• some other catalogued item

So depending on context, English might translate it more naturally as:

• publication
• item
• library material
• sometimes even book, if the context is narrow

A learner should know that the Serbian word may sound a little more administrative or institutional than everyday English publication.

Tek here means something like:

• only
• not until
• only once
• only after

In this sentence, it adds the idea that borrowing is possible only after membership happens.

So:

• Korisnik može da pozajmi publikaciju tek kada se učlani.

means:

• The user can borrow the item only when / only after they become a member.
• The user cannot borrow it before that.

This little word is very important because it sets a restriction.

Učlani se means to become a member, to join, or to enroll as a member.

The base verb is:

• učlaniti se = to join, to become a member

Here učlani is the 3rd person singular present form used in the clause:

• kada se učlani = when they join / when he joins / when she joins / when it joins

Because Serbian often uses perfective present forms in subordinate clauses referring to a future completed event, kada se učlani means:

• when they have joined
• once they become a member
• after joining

So it is not a strange present tense in meaning; it refers to a future completed step.

The verb is učlaniti se, not just učlaniti.

That means it is a reflexive verb in form. In many Serbian verbs, se is simply part of the verb and does not always mean a strongly literal oneself in English.

So:

• učlaniti se = to become a member / to join
• se učlani = joins, becomes a member

English does not use oneself here, but Serbian requires se because that is how the verb is formed.

This is something learners often just need to memorize as part of the verb:

• učlaniti se
• not učlaniti

Literally, kada means when.

But because the verb učlani se is perfective and the sentence describes a condition that must be completed first, the whole phrase naturally comes out in English as:

• when they join
• once they join
• after they become a member

So the Serbian word itself is when, but in context English may prefer once or after for a more natural translation.

Yes.

• kada = full form
• kad = shorter, very common form

Both mean when.

So you could also say:

• Korisnik može da pozajmi publikaciju tek kad se učlani.

This sounds natural too.
Generally:

• kada may feel a bit more formal or careful
• kad is very common in everyday speech

No. Korisnik is grammatically masculine, but it can be used in a generic sense, especially in administrative, legal, or technical language.

So it can mean:

• a male user
• or a user in general, regardless of sex/gender

This is common in Serbian formal style. If someone wanted to make both forms explicit, they might write something like:

• korisnik/korisnica

But in many official sentences, the masculine singular is used generically.

It can be interpreted in a generic way.

Korisnik without an article can mean:

• a user
• the user
• any user / a user in general

Since Serbian has no articles like a and the, the exact interpretation comes from context.

In an institutional sentence like this, the meaning is usually generic:

• A user can borrow a publication only after becoming a member.
• Users may borrow items only after joining.

So English may use either singular or plural depending on style.

That is a very natural Serbian word order.

The structure is:

• Korisnik = subject
• može da pozajmi = verbal phrase
• publikaciju = object
• tek kada se učlani = time/condition clause

Putting the subordinate clause at the end is normal and clear. It lets the sentence first state the main action, then the restriction.

You could rearrange parts for emphasis, but the original order is neutral and natural.

For example:

• Korisnik može da pozajmi publikaciju tek kada se učlani.
  Neutral, standard.

A different order might emphasize the condition more strongly, but the original is what learners should probably copy first.

It is grammatically a time clause with kada (when), but in meaning it also works like a condition.

It tells us the borrowing becomes possible only at the point when membership is completed.

So semantically, it combines both ideas:

• time: when the user joins
• condition: only if/after the user joins

That is why English translations may vary:

• when they join
• once they join
• after they become a member
• only after joining

All of these reflect the same Serbian idea.

Yes, depending on context, that could be a reasonable translation.

The key verb is učlaniti se, which specifically means to become a member. So the most exact translations are:

• join
• become a member
• enroll as a member

But in some real-world contexts, especially on websites, in libraries, or in systems with accounts, English might choose:

• register
• sign up
• enroll

if that sounds more natural.

Still, the Serbian wording points most directly to membership, not just general registration.