Moj otac radi u kancelariji.

• moj = my
• otac = father
• radi = works / is working
• u = in / at
• kancelariji = office

Grammatically:

• moj otac is the subject: my father
• radi is the verb
• u kancelariji is a prepositional phrase showing location: in the office / at the office

So the structure is basically:

[subject] + [verb] + [location]

Because moj has to agree with otac.

In Serbian, possessive words like moj change for:

• gender
• number
• case

otac is:

• masculine
• singular
• nominative here

So the correct form is moj.

Compare:

• moj otac = my father
• moja majka = my mother
• moje dete = my child

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

In Serbian, the subject of a sentence is normally in the nominative case.

So:

• otac = nominative singular
• if it had another role in the sentence, it might change form

For example:

• Moj otac radi. = My father works.
• Vidim svog oca. = I see my father.

Here, since father is the one doing the action, otac stays in the nominative.

Radi is the 3rd person singular present tense of raditi = to work.

That means:

• ja radim = I work
• ti radiš = you work
• on/ona radi = he/she works

Since otac = he, Serbian uses radi.

Depending on context, the English translation can be:

• works
• is working

Serbian present tense often covers both ideas.

Because u can take different cases depending on meaning.

Here it expresses location: where someone works.
So u uses the locative:

• u kancelariji = in the office / at the office

If it expressed motion toward a place, Serbian would usually use the accusative:

• Idem u kancelariju. = I am going to the office.

So the contrast is:

• u + locative = being in a place
• u + accusative = going into/to a place

That is why kancelariji is correct here.

Because after u in the meaning of location, the noun goes into the locative case.

The dictionary form is:

• kancelarija = office

Its locative singular is:

• kancelariji

So:

• u kancelariji = in the office

This is a common pattern for many feminine nouns ending in -a:

• škola → u školi
• soba → u sobi
• kancelarija → u kancelariji

Yes, Serbian could say Otac radi u kancelariji, but the meaning changes slightly in feel.

• Moj otac radi u kancelariji. = My father works in an office / at the office.
• Otac radi u kancelariji. = Father works in an office / at the office.

Including moj makes the possession explicit, just like in English my father.

In Serbian, possessives are sometimes omitted when the relationship is obvious from context, especially in family contexts, but moj otac is completely normal and often clearer for learners.

It can mean either, depending on context.

In Serbian, the present tense often covers both:

• a general fact
• an action happening now

So Moj otac radi u kancelariji can mean:

• My father works in an office (general fact)
• My father is working in the office only if the context strongly supports that meaning

Without extra context, most people will understand it as a general statement: My father works in an office.

Yes. Serbian word order is more flexible than English, because case endings show grammatical roles.

The most neutral order here is:

• Moj otac radi u kancelariji.

But other orders are possible for emphasis, for example:

• U kancelariji radi moj otac. = It is my father who works in the office / My father works in the office.
• Radi moj otac u kancelariji. = possible, but more marked or contextual

Even though other orders are possible, the original sentence is the best basic pattern for a learner.

Otac is the standard word for father. It is correct and neutral.

In everyday speech, many people also say:

• tata = dad

So:

• Moj otac radi u kancelariji. = more neutral / standard
• Moj tata radi u kancelariji. = more everyday / family-like

A learner should know both, but otac is perfectly natural.

A rough pronunciation guide for an English speaker is:

moy OH-tats RAH-dee oo kan-tseh-lah-REE-yee

A few useful points:

• j is pronounced like English y
  • moj sounds like moy
• c is pronounced like ts
  • otac ends with ts
• r is rolled or tapped
• č / ć / dž / đ / š / ž are important Serbian sounds, but none of those appear here except the plain c
• ji in kancelariji is pronounced clearly, not merged into an English j sound

This does not capture the accent perfectly, but it is a good starting point.