Learn Hardcore Croatian: Kad budemo završili večeru, spremit ćemo piletinu u hladnjak za sutra. - When we finish dinner, we’ll put the chicken in the fridge for tomorrow.

Croatian often uses the future perfect (also called futur II) after time conjunctions like kad (when) to express “when we have finished / once we finish”.

kad budemo završili = when we (will) have finished (the finishing happens before the main future action)
kad ćemo završiti is generally not used in this kind of subordinate time clause.
You can also hear kad završimo (večeru) in everyday speech, but kad budemo završili is the more explicit “finished before the next thing” structure.

What exactly is the tense in budemo završili?

It’s futur II (future perfect) formed with:

present of biti: budem, budeš, bude, budemo, budete, budu
past active participle: završio/završila…, here završili (plural)

So: budemo završili = we will have finished.

Why is završili in plural masculine form?

The participle agrees with the subject we (mi), which is plural. In mixed-gender or unspecified groups, Croatian defaults to the masculine plural participle:

mi (mixed/unspecified) → završili
If it’s explicitly all-female, you’d use završile.

Why is the verb split like spremit ćemo? Can I also say ćemo spremiti?

Yes, both are possible. Ćemo is a clitic (unstressed auxiliary) and typically takes the second position in its clause.

spremit ćemo piletinu… (very common)
piletinu ćemo spremiti… (also common; emphasizes piletinu)
The form ćemo spremiti is fine when something comes before it (so ćemo is still “second”): e.g. Sutra ćemo spremiti piletinu…
But starting a sentence with Ćemo is usually avoided in standard style.

What’s the difference between spremit ćemo and spremit ćemo se?

spremiti (nešto) = to put away / store / prepare something
spremiti se = to get ready / prepare oneself
Here it’s spremit ćemo piletinu = we’ll put the chicken away.

Why is there a comma after večeru?

Because the sentence begins with a subordinate time clause:
Kad budemo završili večeru, (When we’ve finished dinner,)
then comes the main clause. Croatian punctuation matches English here.

Why is it večeru and not večera?

Večera is the dictionary form (nominative). After završiti (to finish), the thing finished is the direct object, so it’s in the accusative:

završiti večeru = finish dinner
Hence večeru.

Why is it piletinu (accusative) and not some other form?

Because spremiti here takes a direct object (what you’re putting away). Direct objects are typically accusative:

spremiti (što?) piletinu = put away the chicken / some chicken
Also, piletina is often a mass/food noun, and the accusative singular is piletinu.

Does piletinu mean “the chicken” or “some chicken”?

Croatian doesn’t have articles (a/the), so piletinu can mean either depending on context:

the chicken (the chicken we just ate / cooked)
some chicken (unspecified amount)
In this sentence, context strongly suggests the (leftover) chicken from dinner.

Why is it u hladnjak and not u hladnjaku?

After u:

u + accusative expresses motion into something (destination): u hladnjak = into the fridge
u + locative expresses location inside something (where something is): u hladnjaku = in the fridge
Here we’re putting it into the fridge, so accusative is used.

Is hladnjak the only word for “fridge”? What about frižider?

Both are used:

hladnjak = more standard/formal Croatian
frižider = very common colloquially (a loanword)
The sentence is perfectly natural with either: u hladnjak / u frižider.

What does za sutra mean here—“for tomorrow” or “until tomorrow”?

Here za sutra means for tomorrow (intended use/time): we’re storing it so it can be eaten tomorrow.
If you wanted more of an “until tomorrow” time limit, you’d more likely express it differently depending on context (often still possible with do sutra = until tomorrow).