Ogrlica je na stolu.

Because na stolu expresses location: the necklace is on the table.

After the preposition na, Serbian uses different cases depending on meaning:

• na + locative = location, where something is
  
  • na stolu = on the table
• na + accusative = direction or movement toward a surface
  
  • na sto = onto the table

So in Ogrlica je na stolu, stolu is the locative singular form of stol.

Je is the 3rd person singular present form of the verb biti (to be).

So here it means is:

• Ogrlica je na stolu. = The necklace is on the table.

A useful thing to know is that je is a clitic, which means it usually appears in the second position in the sentence.

Serbian has no articles.

So:

• ogrlica can mean a necklace or the necklace
• stolu can mean a table or the table, depending on context

English forces you to choose between a and the, but Serbian usually leaves that to context.

Ogrlica is in the nominative singular, because it is the subject of the sentence.

The basic dictionary form is:

• ogrlica = necklace

In this sentence, it is the thing being described, so nominative is the expected case.

Ogrlica is feminine.

A very common pattern in Serbian is:

• nouns ending in -a are often feminine

So:

• ogrlica = feminine singular noun

This matters for adjectives and past-tense forms, for example:

• Lepa ogrlica = A beautiful necklace
• Ogrlica je bila skupa = The necklace was expensive

Because na means on in this context, while u usually means in.

Compare:

• na stolu = on the table
• u kutiji = in the box

So if the necklace is resting on the surface of the table, na is correct.

Yes. Serbian word order is more flexible than English, although not completely free.

The neutral order here is:

• Ogrlica je na stolu.

But you can also say:

• Na stolu je ogrlica.
  This puts more focus on where it is.

The meaning stays basically the same, but the emphasis changes.

One thing to remember: the clitic je usually stays near the beginning, in second position.

A rough English-friendly pronunciation would be:

• Ogrlica ≈ OH-grlee-tsa
• je ≈ yeh
• na ≈ nah
• stolu ≈ STOH-loo

So the whole sentence sounds roughly like:

• OH-grlee-tsa yeh nah STOH-loo

A few letter notes:

• j is pronounced like English y
• c is pronounced like ts
• r is rolled or tapped more than in English

If you mean location, you say:

• Ogrlica je na stolu. = The necklace is on the table.

If you mean movement toward the table, the structure changes. For example:

• Stavljam ogrlicu na sto. = I am putting the necklace onto the table.

Notice the difference:

• na stolu = on the table, already there
• na sto = onto the table, movement toward it

This is a very important Serbian pattern after prepositions like na.

Not always. In many varieties of Serbian, sto is very common as the basic word for table, while stol may sound regional, literary, or more common in some neighboring standard varieties.

So learners may also encounter:

• Ogrlica je na stolu.

where the locative stolu can correspond to a nominative form learners may see as sto or stol, depending on usage and dictionary style.

The key thing for this sentence is that na stolu is a normal form meaning on the table.

If you want to say The necklaces are on the table, you would say:

• Ogrlice su na stolu.

Changes:

• ogrlica → ogrlice = plural
• je → su = are

So:

• Ogrlica je na stolu. = The necklace is on the table.
• Ogrlice su na stolu. = The necklaces are on the table.