Learn Hardcore Croatian: Kada netko priča šalu za stolom, teta se prva počne smijati. - When someone tells a joke at the table, my aunt is the first to start laughing.

In Croatian, kada (or kad) with the present tense is very commonly used for general truths and habitual actions, just like English uses the present simple:

Kada netko priča šalu za stolom, teta se prva počne smijati.
= Whenever / when someone tells a joke at the table, aunt is the first to start laughing.

Here, priča and počne are in the present tense, but the meaning is general and habitual.

You can use other tenses with kada:

Kada je netko pričao šalu za stolom, teta se prva počela smijati.
When someone was telling a joke at the table, aunt was the first to start laughing. (past habit in a narrative)
Kada netko bude pričao šalu za stolom, teta će se prva početi smijati.
When someone tells a joke at the table (in the future), aunt will be the first to start laughing.

So the present tense here is natural Croatian for a general, repeated situation.

What is the difference between kada and kad?

Kada and kad are essentially the same word; kad is just a shorter, more colloquial form.

Both mean when (in the temporal sense):

Kada / Kad dođeš, javi se.
When you come, let me know.

You can freely replace kada with kad in this sentence:

Kad netko priča šalu za stolom, teta se prva počne smijati.

In formal writing, kada is slightly more common, but kad is not wrong and is very frequent in spoken language.

What exactly does netko mean, and how is it different from neko or itko?

Netko means someone or somebody (an unspecified person):

Netko kuca na vrata. – Someone is knocking at the door.

In many dialects and in casual speech, people say neko instead of netko; it is a colloquial variant. Standard Croatian prefers netko, but you will hear neko a lot.

Itko means anyone (usually in questions or negatives):

Ima li itko ovdje? – Is there anyone here?
Ne poznajem itko is wrong; it should be:
Ne poznajem nikoga. – I do not know anyone.

So in your sentence, netko is the correct choice because it translates to someone:

Kada netko priča šalu… – When someone tells a joke…

Why is it priča šalu and not something like govori šalu? Is pričati the normal verb for telling jokes?

Yes. For telling stories, jokes, or anecdotes, Croatian normally uses pričati (to tell, to relate, to narrate):

pričati priču – to tell a story
pričati vic – to tell a joke
pričati šalu – to tell a joke

Govoriti is more neutral to speak / talk / say, often about language or speech in general, not about storytelling:

Govoriti polako. – To speak slowly.
Govoriti engleski. – To speak English.

So pričati šalu is idiomatic, while govoriti šalu sounds odd or non‑native.

Why is šalu used instead of šala?

Šala is a feminine noun. In the sentence, it is the direct object of priča (what is being told), so it must be in the accusative case:

Nominative (dictionary form): šala – a joke
Accusative (object): šalu – a joke (as object)

Pattern for many feminine nouns ending in -a:

knjiga → knjigu (I read a book – Čitam knjigu.)
pjesma → pjesmu (I sing a song – Pjevam pjesmu.)
šala → šalu (He tells a joke – Priča šalu.)

So priča šalu is grammatically required: the verb pričati takes a direct object in the accusative.

What does za stolom literally mean, and why is it not na stolu?

Za stolom literally is behind/at the table, and in this context it means at the table, i.e. people sitting around the table.

za
- instrumental (here: stolom) → location at / behind something:
  - sjediti za stolom – to sit at the table
  - raditi za računalom – to work at the computer

Na stolu means on the table (physically on the surface), with na + locative:

Čaša je na stolu. – The glass is on the table.

Contrast:

pričati šalu za stolom – to tell a joke while sitting at the table (during a meal, gathering, etc.)
ostaviti knjigu na stolu – to leave the book on the table.

Also notice the case:

za stol (accusative) – motion towards the table: Sjedamo za stol. – We are sitting down at the table.
za stolom (instrumental) – location: Sjedimo za stolom. – We are sitting at the table.

What does teta mean here? Is it only a biological aunt?

Teta literally means aunt, but in everyday Croatian it has broader, informal uses:

Biological or marital aunt
- Teta mi živi u Zagrebu. – My aunt lives in Zagreb.
A familiar way to refer to an older woman (especially to children)
- Adults may say to a child: Reci teti hvala. – Say thank you to the lady.
In kindergartens, teta is often used for female preschool teachers or carers.

In your sentence, teta is likely a specific family aunt, but context could also make it “that lady at the table”. The important grammatical point: teta is feminine, so the adjective prva must agree with it (not prvi).

Why is it smijati se and not just smijati? What does the se do?

Smijati se is a reflexive verb meaning to laugh. The reflexive pronoun se is an essential part of the verb; without se, smijati on its own is either rare or has different meanings in some expressions.

So, you normally say:

smijati se – to laugh
- Teta se smije. – Aunt is laughing.
- Počela se smijati. – She started laughing.

The se does not literally mean herself here; it is just required by the verb, similar to French se laver or Spanish reírse.

In your sentence, the full infinitive is smijati se, but because se is a clitic (an unstressed little word), it moves earlier in the sentence:

Basic: početi se smijati – to start laughing
In the sentence: teta se prva počne smijati

So se belongs with smijati se, not with početi.

Why is it teta se prva počne smijati and not teta počne se smijati? Where does se have to go?

In Croatian, se is a clitic. Clitics normally move to the “second position” in the clause (after the first stressed word or phrase). That is a fixed word‑order rule.

The core phrase is:

početi se smijati – to start laughing

But in a full sentence, clitics like se move:

Teta se prva počne smijati. ✅
Teta počne se smijati. ❌ (sounds wrong to native speakers)

Other acceptable variations that respect clitic position:

Prva se teta počne smijati. (emphasis on first)
Kad netko priča šalu za stolom, ona se prva počne smijati.

The basic rule: se should come very early in the clause, usually right after the first word or phrase, not stuck between počne and smijati.

Why is it prva and not prvo? What is the difference between these forms?

Prvi, prva, prvo are forms of the ordinal first and must agree with the noun in gender and number:

Masculine: prvi
Feminine: prva
Neuter: prvo

Since teta is feminine, you need prva:

teta je prva – the aunt is the first (one)

Here prva is used almost like a pronoun meaning the first one, referring back to teta:

Teta se prva počne smijati.
Literally: Aunt herself, as the first one, starts to laugh.

Prvo can be used as neuter, or as an adverb meaning first / firstly:

Prvo operi ruke, onda jedi. – First wash your hands, then eat.

In your sentence, you are not saying firstly she starts to laugh, but she is the first (person) to start laughing, so prva is correct.