Povratna karta je neverovatno skupa.

Because karta is a feminine singular noun, and the adjective has to agree with it in gender and number.

• masculine: skup
• feminine: skupa
• neuter: skupo

So:

• skup hotel = an expensive hotel
• skupa karta = an expensive ticket
• skupo vino = expensive wine

In this sentence, skupa refers back to karta, so it must be feminine singular.

Povratna karta means a return ticket or round-trip ticket.

The adjective povratna comes from povratan, meaning something like return or for going back. Together with karta, it forms a very common travel expression.

Compare:

• karta = ticket
• jednosmerna karta = one-way ticket
• povratna karta = return ticket

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

So the structure is:

• Povratna karta = the return ticket / a return ticket
• je = is
• neverovatno skupa = unbelievably expensive

This is a very standard Serbian sentence pattern: noun + je + adjective/adverbial phrase.

For example:

• Hotel je skup. = The hotel is expensive.
• Soba je mala. = The room is small.

Serbian does not have articles like the or a/an.

So karta can mean:

• a ticket
• the ticket

The exact meaning depends on context.

That is why Povratna karta je neverovatno skupa could be understood as:

• The return ticket is unbelievably expensive or
• A return ticket is unbelievably expensive

In many learning materials, English uses the because it sounds natural in context, but Serbian does not mark that difference with an article.

Because neverovatno is functioning as an adverb here, modifying the adjective skupa.

It means unbelievably, incredibly, or amazingly.

Adverbs do not agree with nouns in gender or number, so neverovatno stays the same.

Compare:

• neverovatno skup hotel = an unbelievably expensive hotel
• neverovatno skupa karta = an unbelievably expensive ticket
• neverovatno skupo putovanje = an unbelievably expensive trip

The adjective changes:

• skup / skupa / skupo

But the adverb stays:

• neverovatno

Yes, Serbian word order is fairly flexible, but not every version sounds equally natural in every context.

The neutral word order here is:

• Povratna karta je neverovatno skupa.

You could also hear:

• Povratna karta je skupa.
• Neverovatno je skupa povratna karta.
• Skupa je povratna karta.

These alternatives usually change the focus or emphasis rather than the basic meaning.

For a learner, the original order is the safest and most natural standard pattern.

In this sentence, skupa clearly means expensive.

The adjective skup / skupa / skupo normally means expensive in everyday Serbian:

• skup auto = an expensive car
• skupa karta = an expensive ticket

In some contexts, especially in forms of address like draga or dragi, Serbian uses different words for dear in the emotional sense. So here you should definitely understand skupa as expensive, not beloved.

It is in the nominative singular.

Why?

Because povratna karta is the subject of the sentence:

• Povratna karta = the return ticket
• je neverovatno skupa = is unbelievably expensive

Both povratna and karta are feminine singular nominative forms.

This is the dictionary form of the noun:

• karta

And the adjective agrees with it:

• povratna karta

Yes, absolutely.

Neverovatno skupa means something stronger, like:

• unbelievably expensive
• incredibly expensive

But Serbian has many common intensifiers, including:

• vrlo skupa = very expensive
• jako skupa = very/really expensive
• baš skupa = really expensive
• neverovatno skupa = unbelievably expensive

So the original sentence sounds a bit more emphatic than just very expensive.

They are related.

• verovati = to believe
• verovatan = believable / probable
• neverovatan = unbelievable / incredible
• neverovatno = unbelievably / incredibly, or sometimes unbelievable depending on function

In your sentence, neverovatno is being used adverbially, so it means something like unbelievably.

This kind of word family is very useful in Serbian, because once you know the root ver-, you can recognize several related words.

In standard Serbian, in a sentence like this, je is normally kept:

• Povratna karta je neverovatno skupa.

Omitting it would usually sound incomplete or poetic rather than normal everyday speech.

However, Serbian sometimes drops forms of to be in certain styles, headlines, or very informal speech, but for learners, you should treat je here as necessary.

In Cyrillic, it is:

Повратна карта је невероватно скупа.

This is exactly the same sentence, just written in the other Serbian script.

Serbian is commonly written in both:

• Latin: Povratna karta je neverovatno skupa.
• Cyrillic: Повратна карта је невероватно скупа.

A rough pronunciation guide for an English speaker is:

POV-rat-na KAR-ta ye ne-ve-ro-VAT-no SKOO-pa

A few helpful points:

• j in Serbian is like English y, so je sounds like ye
• v is always a real v
• r is rolled or tapped
• u is like oo in food
• stress is not marked in normal spelling, but learners can safely say it approximately as above and still be understood

The spelling is quite phonetic, so once you know the sound values of the letters, reading Serbian gets much easier.