U petak popodne sam zauzeta.

In this sentence, u petak means on Friday.

Even though u often means in, with days of the week it can be used to mean on in the sense of time. So:

• u petak = on Friday
• u ponedeljak = on Monday
• u subotu = on Saturday

This is a very common time expression in Serbian.

Because after u in this time expression, petak stays in the accusative, and for this masculine inanimate noun, the accusative form is the same as the nominative:

• nominative: petak
• accusative: petak

So u petak is the expected form.

Popodne means afternoon.

In u petak popodne, it works as part of a time expression meaning on Friday afternoon.

You can think of it as adding more detail to u petak:

• u petak = on Friday
• u petak popodne = on Friday afternoon

Serbian often expresses time more compactly than English.

Instead of something like on Friday in the afternoon, Serbian naturally says:

• u petak popodne

This is normal and idiomatic. You do not need an additional preposition before popodne here.

Sam is the 1st person singular form of the verb biti (to be) in the present tense.

So:

• ja sam = I am

In this sentence, sam means am.

The full sentence literally matches:

• u petak popodne = on Friday afternoon
• sam = am
• zauzeta = busy

This is because Serbian has special unstressed words called clitics, and sam is one of them.

Clitics usually go in the second position of the sentence or clause, not necessarily right after the subject. So Serbian word order often looks different from English.

That is why:

• U petak popodne sam zauzeta.

is completely natural.

If you added ja, it would usually be:

• U petak popodne ja sam zauzeta.

But the pronoun ja is often omitted because the verb already shows the person.

Because Serbian often drops subject pronouns when they are not necessary.

The form sam already tells you the subject is I. So:

• sam = I am

That makes ja optional. Serbian uses ja only when it is needed for emphasis, contrast, or clarity.

So both are possible:

• U petak popodne sam zauzeta.
• U petak popodne ja sam zauzeta.

The version without ja is very natural.

Because zauzeta is the feminine singular form of the adjective, and it agrees with the speaker.

So this sentence is said by a woman.

• zauzet = busy, masculine singular
• zauzeta = busy, feminine singular
• zauzeto = busy, neuter singular

If a man were speaking, he would say:

• U petak popodne sam zauzet.

Yes, zauzet / zauzeta can mean more than one thing depending on context.

Common meanings include:

• busy
• occupied
• sometimes taken or reserved

In this sentence, the meaning is clearly busy.

Yes, it is a natural and correct way to say it.

A very close English-style breakdown would be:

• U petak popodne sam zauzeta. = I’m busy on Friday afternoon.

Serbian word order is flexible, so you may also hear variations such as:

• Sam zauzeta u petak popodne.
• Zauzeta sam u petak popodne.

But U petak popodne sam zauzeta is clear, natural, and very common.

Yes. Popodne and posle podne are closely related, and both can refer to the afternoon.

However, popodne is very common and compact, and in this sentence it sounds very natural:

• U petak popodne sam zauzeta.

So for a learner, popodne is an excellent form to know and use.

For a beginner, the most important thing is to pronounce each word clearly:

• u
• petak
• popodne
• sam
• zauzeta

A useful point is that z in zauzeta is pronounced like z in zoo, and j in Serbian is pronounced like English y. So if you ever see forms like zauzeti or ja, remember that j has a y sound.

You do not need perfect pitch accent to be understood; getting the vowels and consonants right matters much more at this stage.