Ljubičasta šalica je na stolu u kuhinji.

Because ljubičasta has to agree with šalica in gender, number, and case.

• šalica is feminine
• it is singular
• here it is in the nominative case, because it is the subject of the sentence

So the adjective also takes the feminine singular nominative form:

• masculine: ljubičast
• feminine: ljubičasta
• neuter: ljubičasto

That kind of adjective agreement is very important in Croatian.

Šalica usually means a cup or sometimes a small mug, depending on context. Very often it suggests something like a tea cup or coffee cup.

A related word is čaša, which means glass.

So:

• šalica = cup
• čaša = glass

Je is the 3rd person singular present tense of biti (to be), meaning is.

So:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is

In this sentence, šalica is singular, so Croatian uses je:

• Ljubičasta šalica je... = The purple cup is...

Because na can take different cases depending on whether you mean location or movement.

Here the cup is already located on the table, so Croatian uses the locative case:

• stol = table
• na stolu = on the table

Compare:

• Šalica je na stolu. = The cup is on the table.
  
  • location → locative
• Stavljam šalicu na stol. = I am putting the cup onto the table.
  
  • movement toward a place → accusative

This location-vs-movement distinction is very common after na and u.

Because stol is in the locative singular after na when it means location.

Basic form:

• stol = table

Locative singular:

• stolu = on the table / about the table, depending on context

So:

• na stolu = on the table

This is just the case ending required by the preposition and meaning.

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

• kuhinja = kitchen
• u kuhinji = in the kitchen

Compare:

• Šalica je u kuhinji. = The cup is in the kitchen.
  
  • location → locative
• Nosim šalicu u kuhinju. = I am carrying the cup into the kitchen.
  
  • movement toward the kitchen → accusative

So:

• u kuhinji = in the kitchen
• u kuhinju = into the kitchen

Because kuhinja is a feminine noun, and here it is in the locative singular.

• nominative: kuhinja
• locative: kuhinji

So after u meaning in, you get:

• u kuhinji = in the kitchen

This kind of noun ending change is one of the main things learners need to get used to in Croatian.

Croatian normally does not use articles like English a and the.

So šalica can mean:

• a cup
• the cup

Which one is meant depends on context.

That means Ljubičasta šalica je na stolu u kuhinji. could be understood as:

• The purple cup is on the table in the kitchen
• or sometimes A purple cup is on the table in the kitchen

Usually the situation makes it clear.

Croatian word order is more flexible than English word order.

The neutral order here is:

• Ljubičasta šalica je na stolu u kuhinji.

But other orders are possible, depending on emphasis, for example:

• Na stolu u kuhinji je ljubičasta šalica.
• U kuhinji je ljubičasta šalica na stolu.

These alternatives may sound more natural in specific contexts, especially if you want to emphasize where the cup is.

However, for a learner, the original sentence is a very good standard pattern:

• subject + je + location

Croatian often places short unstressed words, called clitics, near the second position in a clause. Je is one of them.

So in:

• Ljubičasta šalica je na stolu u kuhinji.

the phrase Ljubičasta šalica comes first, and then je appears right after it.

This is very normal in Croatian. You will see the same thing with other clitics too, such as:

• sam
• si
• ga
• mi
• se

It is not exactly the same as English word order, so it is worth paying attention to.

Grammatically, Croatian allows a lot of flexibility, but that version sounds a bit awkward because u kuhinji may seem to describe šalica too late or create a slightly unclear structure.

A clearer version would be:

• Ljubičasta šalica je na stolu u kuhinji.
• Na stolu u kuhinji je ljubičasta šalica.

Those make it clear that the table is in the kitchen and the cup is on that table.

So yes, word order can move around, but not every possible arrangement sounds equally natural.

Yes, you can think of it as a location phrase built in layers:

• na stolu = on the table
• u kuhinji = in the kitchen

Together:

• na stolu u kuhinji = on the table in the kitchen

So the sentence first tells you the object:

• Ljubičasta šalica

and then tells you where it is:

• je na stolu u kuhinji

This is very similar to English structure, even though the Croatian noun endings are different.