Moj otac je sada na poslu.

Because otac is a singular masculine noun, and the possessive adjective moj has to agree with it in gender, number, and case.

• moj = masculine singular
• moja = feminine singular
• moje = neuter singular
• moji = masculine plural

So:

• moj otac = my father
• moji roditelji = my parents

In this sentence, otac is one male person, so moj is the correct form.

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

So here:

• Moj otac = my father
• je = is
• sada = now
• na poslu = at work

Serbian usually does use the verb to be in sentences like this, just as English does:

• On je kod kuće. = He is at home.
• Ona je u školi. = She is at school.

So je is necessary here.

This is a very common feature of Serbian. The short form je is a clitic, which means it usually appears in the second position of the sentence or clause.

So in:

• Moj otac je sada na poslu.

the first unit is Moj otac, and then the clitic je comes right after it.

You will often see this with other short words too, such as:

• sam, si, smo, ste, su
• ga, je, mi, ti, se

For example:

• Moj brat je ovde.
• Ana se smeje.
• Ja sam umoran.

This second-position rule is something English speakers often need time to get used to.

Poslu is in the locative case.

The basic dictionary form is:

• posao = job, work

But after the preposition na when it means at / on in a location sense, Serbian often uses the locative:

• na poslu = at work

So:

• nominative: posao
• locative: poslu

This is why the sentence says na poslu, not na posao.

Compare:

• On je na poslu. = He is at work.
• Pričamo o poslu. = We are talking about work.

Both na and o can require the locative in the right meaning.

This is mostly a matter of fixed usage and how Serbian idiomatically expresses places and states.

Serbian says:

• na poslu = at work
• na fakultetu = at the faculty / at university
• na moru = at the seaside / by the sea

Even though English uses at, Serbian often uses na in these expressions.

By contrast, u is used in many other location phrases:

• u školi = in/at school
• u kući = in the house
• u kancelariji = in the office

So the learner has to memorize many preposition + noun combinations as natural expressions, not translate each preposition word-for-word from English.

Yes. Serbian word order is fairly flexible, although some positions sound more natural than others.

These are all possible:

• Moj otac je sada na poslu.
• Moj otac sada je na poslu. — possible, but less natural in everyday speech
• Sada je moj otac na poslu.
• Moj otac je na poslu sada. — possible, often with special emphasis

The most neutral version here is:

• Moj otac je sada na poslu.

Word order in Serbian often changes to show focus, emphasis, or style, rather than changing the core meaning.

Both mean now.

• sada is the full form
• sad is a very common shorter conversational form

So these are both normal:

• Moj otac je sada na poslu.
• Moj otac je sad na poslu.

In everyday speech, sad is extremely common. Sada may sound slightly fuller, clearer, or a bit more careful, but both are standard.

Yes. Tata is a very common and natural word for dad.

Compare:

• otac = father
  More neutral, formal, or descriptive.
• tata = dad
  More personal, family-like, and everyday.

So:

• Moj otac je sada na poslu. = a bit more neutral/formal
• Moj tata je sada na poslu. = warmer and more conversational

Both are correct; the difference is mainly style and tone.

Yes, you could say Otac je sada na poslu, but it does not sound exactly the same.

• Moj otac clearly means my father
• Otac means father, and depending on context it might mean the father, a father, or just father as a role

Serbian often does not need possessives as often as English does, especially when context is already clear. But in isolation, moj otac is more precise and natural if you specifically mean my father.

So:

• Moj otac je sada na poslu. = clearly My father is at work now.
• Otac je sada na poslu. = possible, but more context-dependent

A simple English-friendly guide:

• otac ≈ OH-tats
• poslu ≈ POHS-loo

A few helpful notes:

• Serbian c is pronounced like ts
• Serbian vowels are usually clear and short:
  • a as in father
  • o as in more (without too much glide)
  • u as in rule

So:

• otac = o-tac with c = ts
• poslu = po-slu

Also, Serbian spelling is very phonetic, so once you learn the sound values of the letters, pronunciation becomes much easier.

Serbian does not have articles like the and a/an, so nouns do not directly show definiteness the way English nouns do.

That means otac can correspond to:

• father
• the father
• sometimes even a father

depending on context.

In this sentence, because of moj, the meaning is naturally specific:

• moj otac = my father

So English uses a possessive, not an article, to make it specific. The Serbian sentence does not need any word corresponding to the.

In standard Serbian, je should be there:

• Moj otac je sada na poslu.

In very casual speech, people may sometimes reduce or weaken short forms in fast conversation, but for learners, you should treat je as required here.

So the correct model sentence is:

• Moj otac je sada na poslu.

It is best not to omit je in this kind of sentence.

Word-for-word, yes, it may look something like on work, but you should not translate it literally.

The natural meaning is:

• na poslu = at work

This is a good example of why Serbian prepositions often need to be learned as part of a whole expression. Literal translation can be misleading.

For learners, it is best to memorize:

• biti na poslu = to be at work

as one natural phrase.