Kad dođu gosti, narezat ću kruh i sir.

Kad means when. It is the shorter, very common form of kada.

In this sentence, kad dođu gosti means when the guests arrive.

The difference between kad and kada is usually just style:

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

In most situations, they mean the same thing.

This is very normal in Croatian.

After time words like kad meaning when, Croatian often uses the present tense of a perfective verb to talk about a future event that will happen before the main action.

So:

• Kad dođu gosti = When the guests arrive
• not literally When the guests are arriving

This is actually similar to English, which also says When the guests arrive, not When the guests will arrive.

Not in this sentence.

Kad će gosti doći? is normally a direct question meaning When will the guests arrive?

But in a time clause like when the guests arrive, Croatian does not usually use the future with će. It uses the perfective present:

• Kad dođu gosti, ... = correct
• Kad će gosti doći, ... = not the normal structure for this meaning

So after kad in this kind of sentence, use dođu, not će doći.

Dođu is the 3rd person plural present form of doći, which means to come / to arrive.

Here it agrees with gosti because gosti is plural:

• gost = guest
• gosti = guests
• dođu = they arrive

This verb is also perfective, which is important here: it refers to a single completed arrival, not an ongoing process.

This is an aspect question.

Croatian often has two related verbs:

• imperfective: focuses on process, repetition, or duration
• perfective: focuses on a completed whole action

Here:

• dolaziti / dolaze = to be coming, to come regularly, to come in progress
• doći / dođu = to arrive, to come as a completed event

In this sentence, the meaning is:

• first the guests arrive
• then I slice the bread and cheese

So the completed arrival is what matters, which is why dođu is the natural choice.

Gosti is nominative plural, because it is the subject of dođu.

Croatian has no articles, so there is no separate word for the or a/an.

That means gosti can mean:

• guests
• the guests

The exact meaning depends on context. In this sentence, English naturally translates it as the guests, but Croatian does not need a separate article to show that.

This is about the future tense and clitic word order.

Croatian future tense is built with:

• the verb
• plus forms of htjeti such as ću

The short form ću is a clitic, which usually wants to be in the second position of its clause.

So in this sentence:

• narezat ću kruh i sir

The first element is narezat, and ću comes right after it.

Also, when the infinitive comes before ću, Croatian normally drops the final -i:

• narezati
  • ću -> narezat ću

So:

• narezat ću = correct
• ću narezati = also possible in a different word order, for example Ja ću narezati kruh i sir
• narezati ću = not standard

Again, this is about aspect.

• rezati = imperfective, to cut, to be cutting, to cut repeatedly
• narezati = perfective, to slice up / cut up, with the idea of reaching a result

In this sentence, the speaker means a one-time completed action in the future:

• I will slice the bread and cheese

That is why narezati is more natural than rezati here.

Yes, they are direct objects, so they are in the accusative case.

However, both kruh and sir are masculine inanimate singular nouns, and for that group the accusative is usually identical to the nominative.

So:

• kruh = nominative
• kruh = accusative
• sir = nominative
• sir = accusative

That is why their forms do not change.

A useful comparison:

• gost is masculine animate
• accusative singular would be gosta, not gost

So Croatian object forms do not always look different; it depends on the noun type.

Yes. That is also correct and very natural.

Croatian word order is fairly flexible. Both of these work:

• Kad dođu gosti, narezat ću kruh i sir.
• Kad gosti dođu, narezat ću kruh i sir.

The difference is mostly about emphasis and information flow:

• Kad dođu gosti puts a little more focus on the event of arriving
• Kad gosti dođu puts gosti earlier and may feel a bit more straightforward to some learners

Both mean the same thing in normal use.

Because Kad dođu gosti is a subordinate time clause, and it is separated from the main clause by a comma.

So the structure is:

• Kad dođu gosti, = subordinate clause
• narezat ću kruh i sir. = main clause

This is standard Croatian punctuation.

You can also put the main clause first:

• Narezat ću kruh i sir kad dođu gosti.

In that version, the subordinate clause comes after the main one.