Który pociąg odjeżdża o szóstej?

Który means which in the sense of choosing one item from a known set.

So Który pociąg...? = Which train...?

Polish learners often confuse który and jaki:

• który = which one
• jaki = what kind / what sort of

So:

• Który pociąg odjeżdża o szóstej? = Which train leaves at six?
• Jaki to pociąg? = What kind of train is it?

Pociąg is in the nominative singular because it is the subject of the sentence.

In other words, the train is the thing that does the action of departing:

• pociąg odjeżdża = the train departs

So Który pociąg odjeżdża o szóstej? literally has the structure:

• Which train
  • departs
    • at six

Odjeżdża means leaves / departs.

It comes from the verb odjeżdżać, which is used for vehicles departing by transport, especially things like:

• trains
• buses
• trams

A helpful comparison:

• jechać = to go / travel by vehicle
• odjeżdżać = to depart, to pull away, to leave

So for a train, odjeżdżać is a very natural verb.

Because Polish, like English, often uses the present tense for scheduled future events.

So:

• Pociąg odjeżdża o szóstej.
  = The train leaves at six.

This is present in form, but future in meaning because it refers to a timetable or schedule.

That is completely normal in Polish.

After the preposition o when talking about a clock time, Polish uses the locative case.

That is why you say:

• o pierwszej = at one
• o drugiej = at two
• o szóstej = at six

Here, szóstej is the locative form.

So o szóstej literally means at the sixth hour.

Yes. You can think of an implied noun such as godzinie (hour), though in normal speech it is usually omitted.

Historically / structurally, it is like:

• o szóstej godzinie = at the sixth hour

In modern Polish, people simply say:

• o szóstej

That is the standard way to say at six o’clock.

The basic word order here is very natural and neutral:

• Który pociąg odjeżdża o szóstej?

Literally:

• Which train
  • departs
    • at six

Polish word order is more flexible than English, so some variation is possible, especially for emphasis. But the given version is the most straightforward and standard.

For a learner, this is the best order to remember.

A rough pronunciation guide:

• Który ≈ KTOO-ri
• pociąg ≈ PO-chyongk
• odjeżdża ≈ od-YEZH-jah
• o szóstej ≈ o SHOOS-tey

A few useful sound notes:

• ó sounds like u
• ą is a nasal vowel, roughly like on/om depending on the sound after it
• sz sounds like English sh
• dż sounds like the j in jam

Also, Polish stress usually falls on the second-to-last syllable:

• koTÓry
• poCIĄG
• odJEŻdża
• SZÓStej

Because Polish has no articles.

English says:

• Which train leaves at six?

Polish simply says:

• Który pociąg odjeżdża o szóstej?

There is no separate word for a or the in Polish. Whether something is definite or indefinite is understood from context.

Yes. In natural English, both of these work:

• Which train leaves at six?
• Which train is leaving at six?

The Polish sentence can cover that same idea. The exact English version depends on context and style, but Which train leaves at six? is the most direct translation.

A typical answer would name the train:

• Pociąg do Krakowa odjeżdża o szóstej.
  = The train to Kraków leaves at six.

Or more briefly:

• Ten pociąg.
  = That train.

Or with a train number:

• Pociąg numer 12 odjeżdża o szóstej.
  = Train number 12 leaves at six.