Ruža je u vazi na stolu.

Not necessarily. It is capitalized here because it is the first word of the sentence.

Croatian, like English, capitalizes the first word of a sentence. So Ruža can simply mean rose here.

That said, Ruža can also be a woman’s name, so without context the form alone could be ambiguous. The meaning shown to the learner tells you which one is intended.

Je is the 3rd person singular present form of biti, meaning to be.

So:

• je = is

In this sentence, it links the subject Ruža with its location:

• Ruža je... = The rose is...

Croatian often does not need an explicit subject pronoun like it or she when the subject is already stated.

Croatian does not have articles.

So where English says:

• a rose
• the rose
• a vase
• the table

Croatian simply uses the noun:

• ruža
• vaza
• stol

Whether something is a or the is understood from context.

So Ruža je u vazi na stolu could correspond to English with a/the depending on the situation.

Because the preposition u here expresses location: in.

When u means in in the sense of being somewhere, it is followed by the locative case.

The noun changes like this:

• vaza = vase
• u vazi = in the vase

So vazi is the locative singular form of vaza.

For the same reason: this sentence describes location, not movement.

With na:

• na + locative = on / at a place
• na + accusative = motion onto something

So:

• na stolu = on the table
• na stol = onto the table

In this sentence, the vase is already there, so Croatian uses the locative:

• na stolu

Both are locative singular forms.

Breakdown:

• vaza → vazi
• stol → stolu

They appear in the locative because they follow prepositions of location here:

• u vazi = in the vase
• na stolu = on the table

This is a very common pattern in Croatian:

• u + locative for being in
• na + locative for being on / at

In this sentence:

• u = in
• na = on

So:

• u vazi = in the vase
• na stolu = on the table

More generally:

• u is used for being inside something
• na is used for being on a surface, and also in some cases at a place

For a learner, the basic meaning here is straightforward:

• the rose is in the vase
• the vase is on the table

The most natural interpretation is:

• the rose is in the vase
• the vase is on the table

So the location is nested:

1. Ruža je u vazi = The rose is in the vase.
2. Vaza je na stolu = The vase is on the table.

Croatian often strings location phrases together like this, just as English can.

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

The sentence given is a natural neutral order:

• Ruža je u vazi na stolu.

But other orders are possible for emphasis or style, for example:

• Na stolu je ruža u vazi.
• U vazi je ruža na stolu.
  though this one may sound less natural depending on context

What usually stays important is the placement of the short unstressed word je, which tends to come near the second position in the clause.

So Croatian word order is not random, but it is more flexible than English.

Because je is a clitic.

Clitics are short unstressed words that usually cannot stand freely in just any position. In Croatian, they typically appear in the second position of the clause.

That is why you get:

• Ruža je u vazi na stolu.

and not usually a neutral sentence like:

• Ruža u vazi je na stolu.

So this sentence also teaches an important Croatian pattern:

• short forms like je tend to come early, usually in second position.

Then Croatian would normally use the accusative after those prepositions, not the locative.

Compare:

Location

• u vazi = in the vase
• na stolu = on the table

Movement toward a place

• u vazu = into the vase
• na stol = onto the table

So the current sentence is clearly about where something is, not where it is going.

The letter ž is pronounced like the s in measure or the g in genre for many English speakers.

So approximately:

• Ruža ≈ ROO-zha

A rough pronunciation guide for the whole sentence:

• Ruža je u vazi na stolu
• ROO-zha ye oo VAH-zee nah STOH-loo

A few notes:

• j is pronounced like English y
• u is like oo
• ž is the zh sound

Yes, it is a complete and natural sentence.

It has:

• a subject: Ruža
• a verb: je
• location phrases: u vazi na stolu

So it is a standard Croatian sentence meaning that the rose is located in the vase on the table.