Moj brat želi da čita knjigu u parku.

Moj means my, and it changes form to agree with the noun it describes. Brat is a masculine singular noun in the nominative case, so the correct form is moj.

Compare:

• moj brat = my brother
• moja sestra = my sister
• moje dete = my child

Želi is the 3rd person singular present tense form of the verb želeti, meaning to want. Since the subject is moj brat = my brother, Serbian uses the he/she/it form: želi.

So:

• ja želim = I want
• ti želiš = you want
• on/ona želi = he/she wants

In Serbian, it is very common to use da + present tense where English uses to + verb. So želi da čita literally looks like wants that he reads, but in natural English it means wants to read.

This is one of the most important Serbian patterns:

• želim da idem = I want to go
• voli da peva = he/she likes to sing
• mora da radi = he/she has to work

Yes, it is the same form, da, but here it has a different job. In this sentence, da is not the word yes. It is a conjunction used to introduce the verb after želi.

So in:

• Da. = Yes.
• želi da čita = wants to read

Same spelling, different meaning and function.

Because after da, Serbian uses a present-tense verb form, not the infinitive. The infinitive is čitati = to read, but after da you say čita.

So:

• čitati = to read
• on čita = he reads / he is reading
• želi da čita = he wants to read

This is about aspect, which is very important in Serbian. Čitati is imperfective, meaning the action is seen as ongoing, repeated, or simply in progress. Pročitati is perfective, meaning to read something through or finish reading it.

In this sentence, želi da čita knjigu means he wants to be reading / wants to read a book, without stressing completion. If you said želi da pročita knjigu, it would mean he wants to finish reading the book.

Because knjigu is the accusative singular form of knjiga. It is the direct object of the verb čita: he is reading a book.

For many feminine nouns ending in -a, the accusative singular changes to -u:

• knjiga → knjigu
• žena → ženu
• soba → sobu

So:

• knjiga = nominative form
• knjigu = accusative form used as the object

Because u can take different cases depending on meaning.

• u + locative = in/at a place, with no movement
• u + accusative = into a place, showing movement

Here, the brother wants to read in the park, so the location is static. That is why Serbian uses the locative: u parku.

Compare:

• On je u parku. = He is in the park.
• Ide u park. = He is going into/to the park.

Yes. Serbian word order is more flexible than English because case endings show the grammatical roles of words. The sentence Moj brat želi da čita knjigu u parku is a neutral, natural order.

But other orders are possible for emphasis, for example:

• U parku moj brat želi da čita knjigu. = emphasis on in the park
• Knjigu moj brat želi da čita u parku. = emphasis on the book

Even though word order can change, the original version is the most straightforward for a learner.