Danas pas nije imao apetit, pa nije htio ni svoju omiljenu poslasticu.

This is the past tense in Croatian, specifically the perfect.

• Positive:
  • imao je = he had
  • htio je = he wanted
• Negative:
  • nije imao = he did not have
  • nije htio = he did not want

In the 3rd person singular, the auxiliary je combines with ne and becomes nije. So you do not say ne je imao.

A useful pattern is:

• je + participle in positive
• nije + participle in negative

So the sentence uses perfectly normal Croatian past-tense negation.

Because these past-tense forms agree with the gender and number of the subject.

The subject here is pas (dog), which is masculine singular, so the participles are:

• imao
• htio

If the subject were feminine singular, you would get:

• Mačka nije imala apetit.
• Nije htjela ni svoju omiljenu poslasticu.

So the ending -o tells you the subject is masculine singular.

Here pa means something like:

• so
• and so
• therefore
• as a result

It links the two clauses:

• Danas pas nije imao apetit
• pa nije htio ni svoju omiljenu poslasticu

So the second part is presented as a consequence of the first part.

It is very common and natural in everyday Croatian.

Here ni means not even.

So:

• nije htio svoju omiljenu poslasticu = he didn’t want his favorite treat
• nije htio ni svoju omiljenu poslasticu = he didn’t even want his favorite treat

It strengthens the negative idea.

In Croatian, ni is often used with a negative verb to add this meaning of not even / neither.

Because svoj is the reflexive possessive pronoun. It is used when the possessor is the same as the subject.

Here the subject is pas, and the treat belongs to that same dog, so Croatian prefers:

• svoju omiljenu poslasticu = his own favorite treat

If you used njegovu, it could sound like you mean someone else’s treat, or at least it would be less natural here.

This is an important Croatian pattern:

• Pas voli svoju igračku. = The dog likes his own toy.
• Pas voli njegovu igračku. = The dog likes his toy, possibly someone else’s male owner’s or another male’s toy, depending on context.

Because they are all in the accusative feminine singular.

The noun poslastica is feminine singular, and here it is the direct object of htio (wanted), so it must be in the accusative:

• Nominative: omiljena poslastica
• Accusative: omiljenu poslasticu

The possessive pronoun and adjective must agree with the noun in:

• gender
• number
• case

So you get:

• svoju
• omiljenu
• poslasticu

all matching each other.

Yes. Htjeti can mean to want, and it can take a direct object noun in the accusative.

So this is normal:

• htio je poslasticu = he wanted a treat

It does not need an extra infinitive here.

Compare:

• Htio je jesti. = He wanted to eat.
• Htio je poslasticu. = He wanted a treat.

Both patterns are possible.

Here apetit is also a direct object, so it is in the accusative singular.

But apetit is a masculine inanimate noun, and in Croatian many masculine inanimate nouns have:

• nominative singular = accusative singular

So:

• Nominative: apetit
• Accusative: apetit

That is why it looks unchanged.

This is the same kind of pattern you see with many masculine inanimate nouns.

Yes, very normal.

• imati apetit = to have an appetite
• nemati apetit / ne imati apetit in meaning = to have no appetite

So:

• pas nije imao apetit = the dog didn’t have an appetite

This is a natural way to express that idea in Croatian.

The dictionary form is htjeti.

Yes, it is somewhat irregular and very common, so it is worth learning early.

Some key forms:

• infinitive: htjeti
• present:
  • hoću = I want
  • hoćeš
  • hoće
• past participle:
  • htio = masculine singular
  • htjela = feminine singular
  • htjeli = masculine plural or mixed plural

So htio in the sentence is the masculine singular past form that agrees with pas.

Yes, it could move. Croatian word order is fairly flexible.

Danas is placed first because it sets the time frame right away:

• Danas pas nije imao apetit...

That is very natural.

Other possible orders include:

• Pas danas nije imao apetit...
• Pas nije imao apetit danas...

These are all possible, but they may sound slightly different in emphasis. Putting danas first highlights today.

Because Croatian has no articles.

So Croatian does not have exact equivalents of English the and a/an.

That means:

• pas can mean a dog or the dog

Context tells you which meaning is intended.

In this sentence, context makes it clear that we are talking about a specific dog, so English naturally uses the dog, but Croatian just says pas.

You could say it, but it is not exactly the same.

• nije imao apetit = didn’t have an appetite
• nije bio gladan = wasn’t hungry

These ideas are close, but not identical.

Someone can:

• be physically not hungry
• or have no appetite because of illness, stress, tiredness, and so on

In this sentence, nije imao apetit works especially well because the second clause says he didn’t even want his favorite treat. That strongly suggests a lack of appetite, not just ordinary fullness.