Learn Hardcore Croatian: Ona je danas zabrinuta jer sin kasni iz škole. - She is worried today because her son is late from school.

Clitics (short, unstressed words like je, sam, si, se, ga, mi) normally go in the second position in the clause.
- So Ona je danas zabrinuta is natural:
  - Ona (1st position), je (2nd), the rest follows.
- Ona danas je zabrinuta is unnatural/wrong in standard Croatian, because je is pushed out of its usual second position.
Other word orders that keep je in second position are fine, with different emphases:
- Danas je ona zabrinuta.
  Emphasis on danas (today) and somewhat on ona (she, as opposed to someone else).
- Danas je zabrinuta.
  Subject ona is dropped because it’s clear from context.

So:

✅ Ona je danas zabrinuta. (neutral)
✅ Danas je ona zabrinuta. (emphasis on “today / she”)
❌ Ona danas je zabrinuta. (breaks clitic position rule)

What is the difference between jer and zato što? Could I replace jer with zato što here?

Both jer and zato što translate as because, but they are used a bit differently.

jer = because (simple, very common)
- Ona je danas zabrinuta jer sin kasni iz škole.
- Sounds natural and neutral.
zato što = literally “for that reason that”, often a bit more emphatic or explanatory
- Ona je danas zabrinuta zato što sin kasni iz škole.
- Also correct and common; the causal relation can feel more highlighted.

In most everyday contexts, you can replace jer with zato što without changing the basic meaning. Jer is shorter and slightly more conversational; zato što can feel a bit more explicit or formal, depending on context.

Why is it just sin and not her son or the son? How would I say her son?

Croatian doesn’t use articles like the or a at all, so sin can mean:

the son, or
a son, or
(her) son – if that’s clear from context.

In Ona je danas zabrinuta jer sin kasni iz škole, the most natural interpretation is her son, because:

We’re talking about her being worried.
In this situation, you normally assume it’s her own child.

If you want to make her son explicit, you can say:

Ona je danas zabrinuta jer njezin sin kasni iz škole.
(njezin = her, long form, more “full”)
Ona je danas zabrinuta jer njen sin kasni iz škole.
(njen = her, very common colloquially)

Also possible and very natural:

Ona je danas zabrinuta jer joj sin kasni iz škole.
Here joj = to her, a dative pronoun that effectively means her son.

What does kasni mean exactly, and what form is it in?

Kasni is the 3rd person singular present tense of the verb kasniti = to be late.

Conjugation of kasniti in the present tense:

(ja) kasnim – I am late
(ti) kasniš – you are late
(on/ona/ono) kasni – he/she/it is late
(mi) kasnimo – we are late
(vi) kasnite – you (pl./formal) are late
(oni/one/ona) kasne – they are late

So sin kasni = the son is late.

In this sentence, kasni iz škole is best understood as he is coming home late from school / he is delayed coming back from school. The verb kasniti is in the present tense but describes a current situation of being late.

Why is it iz škole, and what case is škole in?

Iz means from/out of, and it requires the genitive case.

Nominative (dictionary form): škola (school)
Genitive singular: škole

So:

iz škole = from (the) school

This is the normal way in standard Croatian to say someone is coming from school (as a place).

Examples:

Dolazim iz škole. – I’m coming from school.
Vraća se iz kina. – He/She is coming back from the cinema.

So in the sentence:

sin kasni iz škole = her son is late (coming) from school.

Could you explain a bit more about škole? Why does it end in -e?

Škola is a feminine noun ending in -a in the nominative singular. Its genitive singular form ends in -e.

Declension (singular):

Nominative: škola – school (subject)
Genitive: škole – of the school / from school
Dative: školi – to/for the school
Accusative: školu – (I see) the school
Locative: u školi – in/at the school
Instrumental: školom – with/by means of the school

Since iz requires the genitive, we use škole:

iz škole – from school

Could you explain the difference between iz škole and something like u školi or u školu?

Yes, these combinations express different directions/locations:

iz škole = from school (movement out of the school)
- Sin kasni iz škole. – He is late coming from school.
u školi = in/at school (location, no movement)
- Sin je u školi. – He is at school.
u školu = to school (movement towards school)
- Sin ide u školu. – He is going to school.

So:

iz + genitive → from/out of a place
u + locative → in/at a place
u + accusative → into/to a place

Where can I put danas in the sentence, and does the position change the meaning?

Danas means today and is quite flexible in position. Possible options include:

Ona je danas zabrinuta jer sin kasni iz škole.
Neutral: She is worried today because her son is late from school.
Danas je ona zabrinuta jer sin kasni iz škole.
Slight emphasis on today and she:
- Today it’s she who is worried (maybe yesterday it was someone else), or
- We’re contrasting today with other days.
Ona je zabrinuta danas jer sin kasni iz škole.
Emphasis more on today as the time when she is worried.

All three are grammatically fine. The basic meaning stays the same, but different positions add subtle focus/emphasis. Just remember that the clitic je should stay in second position in the clause.

Should there be a comma before jer? I often see a comma in similar sentences.

In standard Croatian punctuation, it is usual to put a comma before jer when it introduces a subordinate clause of reason:

Ona je danas zabrinuta, jer sin kasni iz škole.

So, from a strictly normative/grammar-book point of view, the comma is recommended.

However, in everyday informal writing (messages, short texts), many native speakers omit this comma, especially in short, simple sentences, and write it as:

Ona je danas zabrinuta jer sin kasni iz škole.

So:

For careful, formal writing: use the comma.
In casual contexts: you will see both versions, and your original sentence will be easily understood.

Can I drop ona or danas and still have a correct sentence? What changes?

Yes, you can drop some elements if they are clear from context.

Dropping ona:
- Je danas zabrinuta jer sin kasni iz škole. – ❌ Wrong; you can’t start with je like that.
- Correct would be something like:
  - Danas je zabrinuta jer sin kasni iz škole.
    (Subject she is implied from context.)
Dropping danas:
- Ona je zabrinuta jer sin kasni iz škole.
  – Correct, just no mention of today. It means:
  She is worried because her son is late from school.

Croatian often drops subject pronouns (ja, ti, on, ona, etc.) when they’re obvious from context, because the verb ending usually shows who the subject is. But in the 3rd person singular (je, kasni), you often rely more on context or include the pronoun for clarity, as in your original sentence.

Is there a more “emotional” or slightly different way to say the same thing in Croatian?

Yes, small changes can add nuance or emphasis. For example:

Danas je jako zabrinuta jer joj sin kasni iz škole.
- jako = very
- joj sin = her son (dative pronoun joj adds a personal touch)
  Meaning: Today she is very worried because her son is late from school.
Danas je zabrinuta, jer se sin opet kasno vraća iz škole.
- opet = again
- kasno vraća = is coming back late
  Meaning: Today she is worried because her son is coming back late from school again.

All these keep the same core situation but adjust intensity or add extra detail.