Autobus za grad polazi u šest sati.

In Croatian, za often does mean for, but with transport and destinations it can also mean bound for / heading to.

So autobus za grad means the bus for the city/town, or more naturally in English, the bus to the city/town.

This is especially common in contexts like:

• timetables
• station announcements
• signs
• general travel language

A close comparison:

• autobus za grad = the bus bound for town/the city
• autobus u grad = the bus going into town

Both can refer to destination, but za grad sounds very natural for a scheduled route or service.

After za in the sense of destination, Croatian uses the accusative case.

The noun grad is a masculine inanimate noun, and for these nouns the accusative singular is the same as the nominative singular.

So:

• nominative: grad
• accusative: grad

That is why you get za grad, not za grada.

You would see grada in other cases, for example:

• iz grada = from the city
• do grada = to/up to the city

Polazi means departs, sets off, or leaves.

It comes from the verb polaziti. In this sentence, it is:

• 3rd person singular
• present tense

So literally:

• autobus ... polazi = the bus departs / leaves

Compared with some similar verbs:

• polaziti = to depart, to set off, often for scheduled departures
• odlaziti = to leave, go away
• kretati (se) = to start moving, set out

In a timetable sentence, polazi is a very natural choice.

Croatian often uses the present tense for scheduled future events, just like English does.

Compare English:

• The bus leaves at six.

Croatian works the same way:

• Autobus za grad polazi u šest sati.

This is especially common for:

• transport schedules
• timetables
• official arrangements
• routines

So even though the departure is in the future, the present tense is completely normal.

Croatian uses u when giving a specific clock time, so:

• u šest sati = at six o'clock

Here u means at, not in.

The word sat means hour or o'clock, and after numbers the form changes. With šest (six), the correct form is sati.

So:

• u jedan sat = at one o'clock
• u dva sata = at two o'clock
• u pet sati = at five o'clock
• u šest sati = at six o'clock

This is a standard time expression.

Yes. In everyday speech, u šest is very common and usually means the same thing as u šest sati.

So both are possible:

• Autobus za grad polazi u šest.
• Autobus za grad polazi u šest sati.

The longer version is a bit fuller and sometimes slightly more formal or explicit. The shorter version is very natural in conversation.

Because Croatian has no articles.

English distinguishes:

• a bus
• the bus

Croatian does not have separate words for a/an/the. So autobus can mean:

• a bus
• the bus

The exact meaning depends on context.

In this sentence, because it sounds like a known scheduled service, English would usually translate it as the bus.

It can mean either city or town, depending on context.

Croatian grad is broader than English city. It often just means an urban place, and in some contexts it can even mean the town centre or into town.

So za grad could be understood as:

• to the city
• to town
• into town

The best English translation depends on the situation.

It can change. Croatian word order is more flexible than English word order.

The sentence as given:

• Autobus za grad polazi u šest sati.

This is a neutral, natural order.

But other orders are also possible, for example:

• U šest sati autobus za grad polazi.
• Autobus za grad u šest sati polazi.

These versions may sound slightly different in emphasis, but the basic meaning stays the same.

In general, Croatian moves words around more freely to highlight:

• time
• contrast
• new information
• topic/focus

Sometimes yes, but it is not exactly the same.

• polazi = departs / sets off
• ide = goes

So:

• Autobus za grad polazi u šest sati.
  = The bus departs at six.

• Autobus za grad ide u šest sati.
  = The bus goes at six.

The second one may be understood, but polazi is better when you mean a scheduled departure time. It is more precise and more typical in transport language.