Learn Hardcore Croatian: Kad idemo iz stana, uvijek zaključamo vrata, a kad se vratimo, prvo ih otključamo. - When we leave the apartment, we always lock the door, and when we return, we first unlock it.

ići = to go (movement in general, often used with destinations or starting points)
odlaziti / otići = to leave, go away (focus on leaving a place)
izlaziti / izići = to go out, exit (focus on going out of an enclosed space)

In everyday speech, Kad idemo iz stana (“When we go from the apartment”) is very natural for “when we leave the apartment.”
You could say Kad odlazimo iz stana or Kad izlazimo iz stana, but they sound a bit more marked or specific. Idemo is a neutral, very common choice for this habitual situation.

Why is it iz stana and not od stana or sa stana?

Croatian prepositions are picky about which verbs and nouns they go with:

iz
- genitive = “out of / from inside” something (an enclosed space, building, room)
od
- genitive = “from” in the sense of origin, distance, or ownership (“from my friend,” “2 km from the city”)
sa
- genitive = “from (off) the surface of” something, or “from” some places (“sa stola” = from the table; “sa posla” = from work)

An apartment (stan) is treated as an enclosed space you go out of, so iz stana = “out of / from the apartment.”
Od stana or sa stana are incorrect here.

Why is it stana and not just stan?

Stan is the basic (nominative) form, but after the preposition iz, Croatian requires the genitive case.

Nominative: stan (the apartment)
Genitive: stana (of the apartment / from the apartment)

Because the phrase is iz + [GENITIVE], you get iz stana.
So the form stana is simply the genitive singular of stan.

What’s going on with vrata? Why is it plural if it means “door”?

In Croatian, vrata is what’s called a pluralia tantum noun:

It’s always plural in form, even if it refers to a single door.
Grammatically: neuter plural (but semantically: “a door / the door”).

So:

vrata su zaključana = the door is locked (literally: doors are locked).

In your sentence, zaključamo vrata = “we lock the door.”
Even though English says “door” in the singular, Croatian uses this fixed plural form vrata.

Why is the pronoun ih used for vrata?

Ih is the 3rd‑person plural pronoun in the accusative/genitive.
Since vrata is grammatically neuter plural, it behaves like “they/them” in Croatian.

“We unlock the door (them)” → otključamo ih.

You might know:

ga = him/it (masc. sing.)
je/ju = her/it (fem. sing.)
ih = them (all genders, plural)

Because vrata is plural, you must use ih, not ga or je.

Could we say otključamo vrata again instead of prvo ih otključamo?

Yes, grammatically you can say:

… a kad se vratimo, prvo otključamo vrata.

Both are correct. The version with ih avoids repeating vrata and sounds very natural and fluent.
Croatian often uses object pronouns (ga, je, ih, etc.) to avoid repeating a noun once it’s clear from context.

Why is it kad se vratimo and not kad vratimo se?

Croatian has “clitics” (short unstressed words) like se, ga, ih, etc., and there’s a strong rule that they tend to appear in second position in the clause.

In kad se vratimo:

kad = 1st element (conjunction)
se = 2nd position clitic
vratimo = main verb

Kad vratimo se breaks that rule and sounds incorrect/unnatural.
So you usually place se right after the first stressed word in the clause, here the conjunction kad.

Why is the verb vratimo se reflexive? What does se add?

The verb vratiti (se) means:

vratiti nešto = to return something
vratiti se = to return / to come back (yourself)

Without se, vratiti needs an object (“return something”):

Vratimo knjigu. = We return the book.

With se, it’s about the subject going back:

Vratimo se kući. = We return home / We come back home.

In your sentence, kad se vratimo = “when we come back (ourselves).” The reflexive se is required for that meaning.

Why are some verbs here perfective (zaključamo, otključamo, vratimo) and others imperfective (idemo)? What’s the difference?

Croatian distinguishes:

Imperfective: ongoing, repeated, or process-focused actions.
Perfective: single, completed actions, or the result.

In the sentence:

idemo (imperfective) – describes the general recurring process “when we go/leave” (habit).
zaključamo / otključamo / vratimo (perfective) – each time this happens, the action is seen as a complete event (we finish locking, we finish unlocking, we (fully) return).

So the structure is: Whenever the process of us going out happens, we perform these complete actions (lock, unlock) as a rule.

Could we say zaključavamo and otključavamo instead of zaključamo / otključamo?

Yes, you could say:

Kad idemo iz stana, uvijek zaključavamo vrata, a kad se vratimo, prvo ih otključavamo.

That uses imperfective verbs for the locking/unlocking too, and it emphasizes the habit (“we (always) do this”) rather than each act as a completed event.

Both versions are grammatical:

Perfective (zaključamo, otključamo) – highlights each lock/unlock as a single completed action.
Imperfective (zaključavamo, otključavamo) – highlights the repeated habit.

In everyday speech, many speakers would actually prefer the imperfective with uvijek (“always”), but the perfective is still acceptable.

The verbs are in the present tense, but it sounds like the future (“when we leave, we’ll lock”). Is that normal?

Yes. In Croatian, with kad (“when”) introducing a time clause, you typically use the present tense even if you’re talking about the future.

So:

Kad idemo iz stana, zaključamo vrata.
literally: “When we go out of the apartment, we lock the door.”
In context it covers: whenever this situation happens (now or in the future), that’s what we do.

If you refer to a specific future event, you still often use the present after kad:

Kad dođeš, nazovi me. = When you come, call me. (both actions in present in Croatian, but future meaning)

What does prvo mean here, and where can it appear in the sentence?

Prvo is an adverb meaning “first / first of all” in a sequence of actions.

In your sentence:

… a kad se vratimo, prvo ih otključamo.
= “and when we come back, first we unlock them.”

Other possible positions:

… a kad se vratimo, ih prvo otključamo. (less common, can sound a bit clumsy)
… a kad se vratimo, najprije ih otključamo. (using najprije = “first / first of all”)

The given word order with prvo before the verb (prvo ih otključamo) is the most natural.

What is the role of a in … vrata, a kad se vratimo …? Could we just say kad se vratimo?

A is a coordinating conjunction that often means something like “and / and then / whereas”, sometimes with a slight contrast or shift.

… zaključamo vrata, a kad se vratimo, …
= “… we lock the door, and (then) when we come back, …”

You could technically drop a:

… zaključamo vrata, kad se vratimo, prvo ih otključamo.

But that sounds less natural and a bit run-on. The a nicely separates the two parts and signals a new stage in the sequence (leaving vs. coming back).

Why is there a comma before a kad se vratimo?

Croatian punctuation requires a comma before coordinating conjunctions like a, i, ali when they join whole clauses (each with its own verb).

Here we have:

Kad idemo iz stana, uvijek zaključamo vrata,
a kad se vratimo, prvo ih otključamo.

Since a introduces another clause with its own verb (vratimo), you separate it with a comma:

…, a kad se vratimo, …

So the comma reflects that you’re joining two independent clauses with a.