Drugi tarifni paket je postpejd.

In this sentence, drugi most naturally means second.

So Drugi tarifni paket je postpejd means The second tariff plan/package is postpaid.

A useful thing to know is that drugi can also mean other or another in some contexts. Serbian uses the same word for both ideas, so context tells you which meaning is intended.

• drugi paket = the second package or another package
• here, because it sounds like part of a list of plans, second is the most likely meaning

Because drugi agrees with paket, and paket is masculine singular.

In Serbian, adjectives change form to match the noun’s:

• gender
• number
• case

Here:

• paket = masculine singular
• so the adjective must also be masculine singular: drugi
• tarifni also matches paket in the same way

Compare:

• drugi paket = second package/plan
• druga tarifa = second tariff
• drugo pitanje = second/another question

Yes, in many real-life contexts tarifni paket means a plan, especially a mobile phone plan or service package.

Literally:

• tarifa = tariff/rate
• tarifni = tariff-related / pricing-related
• paket = package

So tarifni paket is something like:

• tariff package
• pricing plan
• service plan
• often simply plan in natural English

In telecom language, that is a very normal phrase.

Because Serbian does not have articles like English a and the.

So Serbian simply says:

• Drugi tarifni paket je postpejd

and English adds the article when translating:

• The second tariff plan is postpaid

Whether something is the, a, or just general is usually understood from context.

Je means is.

It is the 3rd person singular present form of the verb biti = to be.

So:

• je = is

In this sentence:

• Drugi tarifni paket = the subject
• je = is
• postpejd = postpaid

So the structure is very straightforward:

• X je Y = X is Y

Here postpejd functions like a predicate noun/adjective-like term, meaning postpaid.

It is a borrowing from English, adapted to Serbian spelling. In everyday telecom language, words like postpejd and prepejd are very common.

So:

• postpejd = postpaid
• prepejd = prepaid

In this sentence, postpejd tells you what type of plan the package is.

Because Serbian often adapts borrowed words to match Serbian pronunciation and spelling.

So English postpaid becomes Serbian postpejd.

This spelling reflects how the word is pronounced locally. You may also see English-style spellings in advertising or brand materials, but postpejd is a normal Serbian written form.

The Cyrillic version would be:

• постпејд

The main noun phrase drugi tarifni paket is in the nominative singular.

Why?

Because it is the subject of the sentence.

So:

• drugi = nominative masculine singular
• tarifni = nominative masculine singular
• paket = nominative singular

After je, Serbian often uses a predicate expression in a basic dictionary-like form as well, especially with borrowed terms like postpejd.

For a beginner, the safest takeaway is:

• drugi tarifni paket is nominative because it is the subject

Yes. Serbian word order is more flexible than English word order.

The neutral order here is:

• Drugi tarifni paket je postpejd.

But other orders are possible for emphasis, for example:

• Postpejd je drugi tarifni paket.
• Drugi je tarifni paket postpejd.
  This sounds more marked and context-dependent.

The original order is the most natural if you are simply stating information.

Usually, not in this exact way.

You would normally say:

• tarifni paket je postpejd = the plan is postpaid

rather than:

• postpejd paket

Although in advertising or informal telecom language, shortened expressions like postpejd paket can appear and are understandable.

Still, the sentence you were given uses the very common structure:

• X je postpejd = X is postpaid

It is mostly neutral, but with a modern borrowed telecom term.

• drugi tarifni paket sounds neutral and standard
• postpejd is common in everyday business, telecom, and advertising language

So the whole sentence sounds natural in contexts like:

• phone plan descriptions
• brochures
• websites
• customer service language

It would be:

• Други тарифни пакет је постпејд.

Letter-by-letter:

• Drugi → Други
• tarifni → тарифни
• paket → пакет
• je → је
• postpejd → постпејд

A rough pronunciation guide is:

• Drugi ≈ DROO-gee
• tarifni ≈ ta-REEF-nee
• paket ≈ pa-KET
• je ≈ yeh
• postpejd ≈ POST-payd

A rough full pronunciation:

• DROO-gee ta-REEF-nee pa-KET yeh POST-payd

This is only approximate, but it is close enough to help an English speaker get started.