Korisnik koristi čitaonicu pod uslovom da je članstvo važeće.

Because čitaonicu is the direct object of koristi.

• Base form: čitaonica = reading room
• In this sentence, it becomes čitaonicu because feminine nouns in -a usually take -u in the accusative singular.

So:

• čitaonica = nominative
• čitaonicu = accusative

That is why Korisnik koristi čitaonicu means The user uses the reading room.

Because korisnik is the subject of the sentence, so it stays in the nominative case.

• korisnik = user
• It is a masculine noun, and here it is the one doing the action.

So the structure is:

• Korisnik = subject
• koristi = verb
• čitaonicu = object

Pod uslovom da means provided that, on condition that, or as long as.

It introduces a condition.

Examples:

• Možeš ući pod uslovom da imaš kartu. = You can enter provided that you have a ticket.
• Korisnik koristi čitaonicu pod uslovom da je članstvo važeće. = The user uses the reading room provided that the membership is valid.

Literally, pod uslovom is something like under the condition, and da introduces the clause.

This is a fairly formal expression, common in rules, regulations, and official language.

Yes, but the tone changes.

• ako = if
• pod uslovom da = provided that / on condition that

So:

• Korisnik koristi čitaonicu ako je članstvo važeće.
• Korisnik koristi čitaonicu pod uslovom da je članstvo važeće.

Both are understandable, but pod uslovom da sounds more formal, official, and rule-like. It fits well in notices, library rules, contracts, and policy language.

Because važeće must agree with članstvo.

• članstvo is a neuter singular noun
• Therefore the adjective must also be neuter singular
• So we get važeće

Agreement here is:

• masculine singular: važeći
• feminine singular: važeća
• neuter singular: važeće

Examples:

• dokument je važeći = the document is valid
• dozvola je važeća = the permit is valid
• članstvo je važeće = the membership is valid

Je is the 3rd person singular of biti (to be), and it links the subject and the adjective:

• članstvo je važeće = the membership is valid

In Serbian, when you say that something is something or is in a certain state, you usually use a form of biti.

So:

• članstvo = subject
• je = is
• važeće = valid

Članstvo means membership.

It refers to the state or status of being a member, not the person.

Compare:

• član = member
• članstvo = membership

So this sentence is not saying that the member is valid; it is saying that the membership status/card/registration is valid.

Because Serbian does not use articles like English a/an/the.

So:

• korisnik can mean a user or the user
• čitaonicu can mean a reading room or the reading room
• članstvo can mean membership or the membership

The exact meaning depends on context.

In a sentence like this, korisnik is usually understood in a generic sense:

• a user
• any user
• the user in a rule or policy statement

Yes. Koristi is present tense of koristiti.

In Serbian, the present tense can often cover both:

• uses
• is using

depending on context.

Here, because the sentence sounds like a rule or general statement, koristi is best understood as a general/habitual or regulatory present:

• The user uses / may use the reading room, provided that...

In natural English, you might translate it more idiomatically as:

• A user may use the reading room provided that the membership is valid.

Koristiti means to use and is a very common, neutral verb.

So:

• korisnik koristi čitaonicu = the user uses the reading room

It is related to the noun korisnik:

• koristiti = to use
• korisnik = user

This makes the sentence feel clear and formal.

Depending on context, Serbian could also use other wording, but koristiti is perfectly standard here.

It sounds formal and a little administrative, which is completely natural in the right context.

Why it sounds formal:

• korisnik instead of a more personal word
• pod uslovom da
• the general rule-like structure

This is the kind of sentence you might see in:

• library regulations
• a notice on a wall
• terms of use
• an official website

In casual speech, someone might say something simpler, such as:

• Možeš da koristiš čitaonicu ako ti je članstvo važeće. = You can use the reading room if your membership is valid.

Yes, Serbian word order is fairly flexible, but the original version is the most neutral and clear for formal style.

Original:

• Korisnik koristi čitaonicu pod uslovom da je članstvo važeće.

Possible variation:

• Pod uslovom da je članstvo važeće, korisnik koristi čitaonicu.

That version puts more emphasis on the condition first.

Even though word order can move, case endings still show the grammatical roles, so the meaning remains clear.

It is an adjective, specifically a predicate adjective.

In:

• članstvo je važeće

the adjective važeće describes the subject članstvo after the verb je.

So it is not directly placed before the noun, as in:

• važeće članstvo = valid membership

Both are possible:

• članstvo je važeće = the membership is valid
• važeće članstvo = valid membership

Yes. A very natural alternative is:

• Korisnik koristi čitaonicu uz važeće članstvo.

or

• Korisnik može koristiti čitaonicu ako ima važeće članstvo.

These versions are a bit more direct. The original sentence is still correct, but it sounds more formal and rule-based.

The phrase važeće članstvo simply means valid membership, with the adjective placed directly before the noun.