Kesa je u kolicima.

Kesa is nominative singular. It is the subject of the sentence, so Serbian uses the nominative here.

A useful comparison:

• Kesa je u kolicima. = The bag is in the stroller/cart.
• Vidim kesu. = I see the bag.

In the second sentence, kesu is the direct object, so it changes form.

Also, kesa is a feminine noun, which is why its dictionary form ends in -a.

Je is the 3rd person singular present of biti (to be), so here it means is.

In Serbian, je is a clitic, which means it usually goes in the second position of the sentence or clause.

So:

• Kesa je u kolicima. = normal order
• U kolicima je kesa. = also possible, with different emphasis

It is not always literally the second word, but it normally comes after the first unit of the sentence.

Here u means in, expressing location, so it takes the locative case.

That is why you get:

• u kolicima = in the stroller/cart

So kolicima is the locative plural form of kolica.

A detail that often confuses learners: in the plural, the locative and instrumental forms often look the same. So kolicima could be either form in different contexts, but here it is locative because it follows u in the sense of location.

Because kolica is a plural-only noun in Serbian. Linguists call this pluralia tantum.

That means Serbian normally uses plural forms even when English thinks of it as one item.

This is similar to English words like:

• scissors
• pants

So Serbian says:

• ova kolica = this stroller/cart
• u kolicima = in the stroller/cart

Even though the meaning may refer to one object, the grammar is plural.

This is a very important Serbian pattern:

• u + locative = location (in, inside)
• u + accusative = movement into

So:

• Kesa je u kolicima. = The bag is in the stroller/cart.
• Stavljam kesu u kolica. = I am putting the bag into the stroller/cart.

The first describes where something is.
The second describes where something is going.

Serbian normally does not use articles.

So kesa can mean:

• a bag
• the bag

The exact meaning depends on context.

If Serbian speakers want to be more specific, they can use other words, for example:

• jedna kesa = a/one bag
• ta kesa = that/the bag

But in a simple sentence like Kesa je u kolicima, no article is needed.

Not always. Kolica is a fairly broad word, and the exact meaning depends on context.

For example:

• dečja kolica = baby stroller / pram / pushchair
• kolica za kupovinu = shopping cart / trolley
• invalidska kolica = wheelchair

So in Kesa je u kolicima, the English translation could vary depending on the situation.

Yes. Serbian word order is fairly flexible, because case endings do a lot of the grammatical work.

These are both possible:

• Kesa je u kolicima. = neutral statement
• U kolicima je kesa. = emphasizes the location, or contrasts it with somewhere else

For example:

• U kolicima je kesa, ne na stolu. = The bag is in the stroller/cart, not on the table.

So changing the order usually changes emphasis, not the core meaning.

In standard Serbian, you should normally keep je in a sentence like this:

• Kesa je u kolicima.

Leaving it out can sound incomplete, elliptical, or like a note, caption, or headline rather than a full normal sentence.

So for learners, the safe rule is:

• use je in ordinary present-tense sentences of this kind.