Molim te, pazi da je ključ u torbi prije nego što izađeš.

Here Molim te is the usual informal way to say please to one person.

• molim = I ask / I beg
• te = you (object form, singular informal)

So literally it is something like I ask you, but in normal use it simply functions as please.

If you were speaking to more than one person, or to one person formally, you would say Molim vas instead.

Because Molim te is being used as a polite introductory phrase, set off from the rest of the sentence.

So:

• Molim te, pazi... = Please, make sure...

The comma helps show that Molim te is not part of the main grammar of the clause pazi da..., but a polite addition at the start.

Pazi is the imperative singular of paziti.

Depending on context, paziti can mean:

• watch out
• be careful
• pay attention
• make sure

In this sentence, pazi da... is best understood as make sure that...

So it is not really a warning like be careful! here, but more a reminder to check something.

Because paziti da... is a normal Croatian structure for telling someone to ensure that something is the case.

It often means:

• make sure that...
• see to it that...

A close alternative would be:

• Provjeri je li ključ u torbi... = Check whether the key is in the bag...

The version with pazi da... sounds a little more like don’t forget to make sure...

Because je is a clitic in Croatian. Clitics usually go in the second position of their clause.

So in the clause:

• da je ključ u torbi

the word da comes first, and the clitic je comes right after it.

That is why da je ključ... is natural, while da ključ je... is not the normal word order.

This is a very common Croatian pattern, and English speakers often need time to get used to it.

Je is the 3rd person singular present of biti (to be), in its short clitic form.

So:

• ključ je u torbi = the key is in the bag

Inside the da-clause, it becomes:

• da je ključ u torbi

It is simply the verb is.

Because ključ is the subject of the clause, so it stays in the nominative case.

In:

• da je ključ u torbi

the key is the thing that is in the bag, so ključ is nominative singular.

Torbi is in the locative singular.

After u, Croatian uses:

• locative for location: in / inside
• accusative for motion into something

So:

• u torbi = in the bag (location)
• u torbu = into the bag (movement)

Since the key is being located inside the bag, not moved into it, u torbi is correct.

It is not stated explicitly, because Croatian often drops subject pronouns when the verb ending already shows who the subject is.

Here the forms tell you that the sentence is addressed to one person informally:

• pazi = you (singular, imperative)
• izađeš = you go out / you leave (singular)

So Croatian does not need to say ti unless it wants extra emphasis.

Izađeš is the 2nd person singular present form of the perfective verb izaći (to go out, to leave).

So grammatically it is a present-tense form, but here it refers to a future action:

• prije nego što izađeš = before you leave / before you go out

This is very normal in Croatian.

Because Croatian often uses the present form of a perfective verb in subordinate clauses when referring to a future completed action.

After expressions like:

• kad = when
• ako = if
• čim = as soon as
• prije nego što = before

you will often see this kind of form.

So:

• prije nego što izađeš literally looks present
• but naturally means before you leave

English learners often expect a future form here, but Croatian usually does not use one in this structure.

The important difference is aspect.

• izaći = perfective → one complete action, to go out / to leave
• izlaziti = imperfective → repeated, ongoing, or habitual going out

Here the sentence refers to one specific leaving event, so the perfective verb izaći is the natural choice:

• prije nego što izađeš = before you leave this time

If you used an imperfective form, it would usually sound more habitual or less natural in this context.

Yes, you may also hear shorter variants, especially in speech, such as prije nego.

But for learners, prije nego što is a very safe and standard form to use.

So:

• prije nego što izađeš = very common and clear
• prije nego izađeš = also heard

If you are unsure, stick with prije nego što.

You would change the informal singular forms to formal/plural ones:

• Molim vas, pazite da je ključ u torbi prije nego što izađete.

Changes:

• te → vas
• pazi → pazite
• izađeš → izađete

This can mean either:

• one person addressed formally, or
• more than one person

because Croatian uses the same forms for both.

No. It is natural, but there are other common ways to express the same idea, with slightly different nuance.

For example:

• Molim te, provjeri je li ključ u torbi prije nego što izađeš.
  = Please check whether the key is in the bag before you leave.

• Molim te, pobrini se da ključ bude u torbi prije nego što izađeš.
  = Please make sure the key is in the bag before you leave.

The original pazi da... sounds like a practical reminder. The alternatives may sound a bit more direct or more explicitly about checking.