Kad gosti stignu, sipat ću čaj u sve šalice.

Kad means when.

You can also say kada. The difference is mostly style:

• kad = shorter, very common in everyday speech
• kada = a bit fuller, sometimes slightly more formal or emphatic

So both of these work:

• Kad gosti stignu...
• Kada gosti stignu...

They mean the same thing here.

This is very normal in Croatian.

After time words like kad (when), Croatian usually uses a present form to talk about a future event:

• Kad gosti stignu... = When the guests arrive...

English does something similar:

• natural: When the guests arrive, I’ll pour the tea
• not natural: When the guests will arrive...

So even though stignu looks like present tense, in this kind of clause it refers to a future event.

Stignu is the 3rd person plural present form of stići.

So:

• stići = to arrive, to get there, to reach
• stignu = they arrive

In this sentence, the subject is gosti (guests), so stignu means the guests arrive.

Because gosti is the subject, and subjects are normally in the nominative case.

• gosti = nominative plural = guests / the guests
• goste = accusative plural = used when they are the direct object

Here, the guests are doing the action of arriving, so you need gosti.

Croatian future tense is often made with the infinitive plus the clitic ću.

With many infinitives ending in -ti, when ću comes after the infinitive, the final -i is dropped:

• pisati → pisat ću
• raditi → radit ću
• sipati → sipat ću

So sipat ću is the normal form here.

You may also see:

• ću sipati

That is also possible, but then the full infinitive stays.

Because Croatian future tense uses an auxiliary, here ću, which is a clitic form of htjeti.

So the future is built like this:

• sipati
  • ću → sipat ću

Croatian often splits this kind of future construction, unlike English I’ll pour.

Both of these are possible in Croatian:

• Sipat ću čaj...
• Ja ću sipati čaj...

The version in your sentence is very normal.

Čaj is the direct object of sipat ću, so it is in the accusative singular.

But čaj is a masculine inanimate noun, and many masculine inanimate nouns have:

• nominative singular = accusative singular

So:

• čaj = nominative
• čaj = accusative

That is why the form looks unchanged.

Because u can take different cases depending on the meaning.

Here, the tea is moving into the cups, so Croatian uses u + accusative:

• u sve šalice = into all the cups

If you said u svim šalicama, that would be u + locative, which means location:

• u svim šalicama = in all the cups

So:

• sipati čaj u sve šalice = pour tea into all the cups
• čaj je u svim šalicama = the tea is in all the cups

Because sve has to agree with šalice in gender, number, and case.

Here:

• šalice = feminine plural
• after u with movement, the case is accusative
• feminine plural accusative of sav is sve

So:

• u sve šalice = into all the cups

Compare:

• u svim šalicama = in all the cups (locative plural)
• bez svih šalica = without all the cups (genitive plural)

Because Croatian has no articles.

So nouns like gosti, čaj, and šalice do not need words equivalent to the or a/an.

Croatian relies on context instead:

• gosti can mean guests or the guests
• čaj can mean tea or the tea
• šalice can mean cups or the cups

In this sentence, English naturally uses the guests and the cups, but Croatian does not mark that with articles.

The word order can change.

Croatian word order is more flexible than English, because case endings show the grammatical roles.

For example, these are all possible:

• Kad gosti stignu, sipat ću čaj u sve šalice.
• Sipat ću čaj u sve šalice kad gosti stignu.

The version with Kad gosti stignu first emphasizes the time frame: when the guests arrive.

The given sentence sounds natural and neutral.

No. Sipati means to pour, and it is understandable here.

Depending on style and nuance, Croatian speakers might also use other verbs for liquids, such as:

• uliti
• naliti
• sometimes točiti

But for learning purposes, sipati čaj u šalice is easy to understand and grammatically fine. The main thing to notice in this sentence is the structure:

• Kad + present-form clause
• future tense in the main clause
• u + accusative for movement into something