Popodne sam morala odvesti ljubimca veterinaru, jer je mačka čudno mijaukala.

Sam morala is part of the Croatian past tense.

• sam = the auxiliary to be for I
• morala = the past participle of morati (to have to / must)

Together, sam morala means I had to.

The form morala also tells you the speaker is feminine singular.
If the speaker were masculine, it would be sam morao.

Croatian often leaves out the subject pronoun ja (I) because the verb form already shows the person.

Because sam is a clitic, and Croatian clitics usually go in the second position in the clause.

So in:

Popodne sam morala...

• Popodne is the first element
• sam comes right after it

This is very normal Croatian word order.

You can also say Morala sam... if the sentence begins differently, but once Popodne is placed first, sam naturally follows it.

Here popodne means in the afternoon or that afternoon.

It functions adverbially: it tells you when the action happened.

So:

• Popodne sam morala... = In the afternoon, I had to...

Croatian often uses time words like this without a preposition where English would use in the.

Odvesti is a perfective verb. It suggests a single, completed action: taking the pet to the vet as one whole event.

That fits the situation well:

• morala odvesti = had to take / had to bring

Compare:

• voditi / odvoditi = more imperfective, focusing on the process or repeated action
• odvesti = one completed trip/action

After modal verbs like morati, Croatian still keeps the aspect distinction, so choosing odvesti matters.

Because ljubimca is the accusative singular form of ljubimac (pet).

It is the direct object of odvesti:

• odvesti koga? što? = to take whom? what?
• ljubimca

Since ljubimac refers to an animate being, the accusative singular matches the genitive form:

• nominative: ljubimac
• accusative: ljubimca

This is very common with masculine animate nouns in Croatian.

Veterinaru is dative singular of veterinar.

In this sentence, it shows the destination toward a person:

• odvesti ljubimca veterinaru = take the pet to the vet

Croatian often uses the dative with people in expressions of going/bringing toward someone, similar to:

• ići liječniku
• otići doktoru

You may also hear expressions like kod veterinara, but veterinaru is completely natural here.

Again, this is because je is a clitic.

In the clause:

jer je mačka čudno mijaukala

the conjunction jer (because) comes first, and the clitic je is placed immediately after it.

This is standard Croatian word order.

So:

• jer je mačka... = normal
• jer mačka je... = much less natural in neutral standard word order

Mijaukala is the past participle of mijaukati (to meow).

It agrees with mačka, which is feminine singular:

• mačka = feminine singular
• therefore mijaukala = feminine singular past form

So the form matches the subject grammatically.

Also, mijaukati is imperfective, which fits well here because it describes the cat’s meowing as an ongoing or repeated sound, not one single completed act.

Here čudno is an adverb.

It modifies the verb mijaukala and means strangely / oddly:

• čudno mijaukala = was meowing strangely

The adjective is čudan / čudna / čudno depending on gender, but in this sentence the form is being used adverbially to describe how the cat meowed.

Because Croatian very often drops subject pronouns when they are already clear from the verb form.

In:

sam morala

the person is already understood as I, so ja is unnecessary.

If you added ja, it would usually sound more emphatic:

• Ja sam morala... = I had to... with extra emphasis

So leaving it out is the normal neutral choice.

Because ljubimca is a general word meaning pet, while mačka gives the specific information that the pet was a cat.

So the sentence moves from:

• the pet to
• the cat

This is perfectly natural. English does the same kind of thing:

• I had to take my pet to the vet, because the cat was meowing strangely.

It is not redundant; the second clause simply identifies which pet we are talking about.