Doktorica misli da izostanak neće biti dug, ali želi pričekati točnu dijagnozu.

Croatian does not have articles, so it does not use separate words like the or a/an.

That means:

• doktorica can mean the doctor or a doctor
• izostanak can mean the absence or an absence
• točnu dijagnozu can mean the exact diagnosis or an exact diagnosis

Which one is intended is usually understood from context.

Doktorica is the feminine form meaning female doctor.
Doktor is the masculine form meaning male doctor.

So the sentence tells you that the doctor is female. This is very normal in Croatian, where profession nouns often show gender:

• učitelj / učiteljica
• profesor / profesorica
• glumac / glumica

Here da means that and introduces a subordinate clause:

• Doktorica misli da... = The doctor thinks that...

This is a very common Croatian structure after verbs like:

• misliti = to think
• znati = to know
• reći = to say
• vidjeti = to see

So da izostanak neće biti dug is the content of what she thinks.

Izostanak means absence, being absent, or sometimes a period away from work/school.

In this sentence, it most likely means an absence from work, school, or normal activity due to a medical issue.

Grammatically, izostanak is:

• masculine
• singular
• nominative here, because it is the subject of neće biti

So:

• izostanak neće biti dug = the absence will not be long

Neće biti is the future tense in the negative:

• neće = will not
• biti = be

Together: will not be

More specifically:

• Croatian future tense is usually made with forms of htjeti
  • infinitive
• će is the 3rd person singular future marker
• the negative form is neće

So:

• bit će = it will be
• neće biti = it will not be

A useful thing to notice is that in affirmative future, Croatian often writes bit će, but in the negative it becomes neće biti.

Both words can relate to length, but they are not used in exactly the same way.

In this sentence, dug is the natural choice because it refers to duration:

• dug izostanak = a long absence
• dug sastanak = a long meeting
• dug put = a long journey

Dugačak is more often used for physical length:

• dugačak stol
• dugačka cesta

So izostanak neće biti dug means the absence will not last long.

Because dug agrees with izostanak.

Izostanak is:

• masculine
• singular
• nominative

So the adjective must match it:

• masculine singular nominative: dug
• feminine singular nominative: duga
• neuter singular nominative: dugo

Also, after biti, Croatian usually uses the adjective in nominative in this kind of predicate:

• Izostanak je dug
• Problem je ozbiljan
• Dijagnoza je točna

Because dijagnozu is the direct object of pričekati, so it must be in the accusative case.

Base form:

• točna dijagnoza = nominative

In the sentence:

• pričekati točnu dijagnozu = to wait for the exact diagnosis

The forms are:

• točna → točnu
• dijagnoza → dijagnozu

This is standard feminine singular accusative.

This is mainly about verbal aspect.

• čekati is imperfective: to be waiting, to wait in a general or ongoing sense
• pričekati is perfective: to wait for a bit, to wait until something happens, to hold off until a result

Here pričekati fits well because the doctor wants to wait for one specific thing:

• točnu dijagnozu

So the nuance is something like:

• želi pričekati točnu dijagnozu = she wants to wait until the exact diagnosis is available

If you used čekati, it would sound more ongoing and less goal-oriented.

Because Croatian often uses the infinitive directly after verbs like željeti.

So:

• želi pričekati = wants to wait

This is very common after verbs such as:

• želim ići = I want to go
• mogu doći = I can come
• moramo raditi = we must work

Unlike English, there is no separate word equivalent to to before the infinitive in this structure.

Not completely. Croatian word order is more flexible than English word order, although this sentence uses a very natural, neutral order:

• Doktorica misli da izostanak neće biti dug, ali želi pričekati točnu dijagnozu.

This order sounds standard and unmarked.

Some parts could be moved for emphasis, for example:

• Doktorica misli da neće biti dug izostanak — possible, but less neutral
• Ali želi pričekati točnu dijagnozu — same meaning, with ali starting the clause
• Točnu dijagnozu želi pričekati — puts emphasis on točnu dijagnozu

So the original sentence is probably the best form for ordinary, neutral speech and writing.