Na podwórku dzieci zostawiły rower obok ławki.

Because na podwórku is a prepositional phrase meaning in the yard / in the courtyard. In Polish, when you say where something happens, you usually need a preposition plus the right case ending.

Here, na means location, and podwórko changes to podwórku because it is in the locative case.

The basic form is podwórko. After na when it means location, Polish uses the locative case.

So:

• podwórko = yard, courtyard
• na podwórku = in the yard

This is a very common pattern:

• na stole = on the table
• w domu = in the house
• na podwórku = in the yard

Because Polish and English do not always match prepositions directly. Even though na often means on, with some places Polish uses na where English uses in.

So na podwórku is the normal Polish way to say in the yard / in the courtyard. It is something you largely have to learn as a set expression.

Dzieci is plural. It means children.

Its singular form is dziecko = child.

So:

• dziecko = child
• dzieci = children

This is an irregular noun, so learners usually just memorize both forms.

Because dzieci takes non-masculine-personal plural agreement in Polish grammar.

In the past tense, Polish plural forms distinguish:

• -li for masculine personal groups
• -ły for non-masculine-personal groups

Even though children are people, the noun dzieci grammatically behaves like a non-masculine-personal plural noun, so you say:

• Dzieci zostawiły...

not

• Dzieci zostawili...

This is one of the trickier agreement patterns in Polish.

This is about aspect.

• zostawiły comes from zostawić and is perfective
• zostawiały comes from zostawiać and is imperfective

Here, the sentence describes a completed action: the children left a bicycle there. That is why Polish uses the perfective verb zostawiły.

Very roughly:

• zostawiły = they left it, the action is completed
• zostawiały = they were leaving it / used to leave it, focusing more on process or repetition

It is changing case, but for this type of noun, the accusative looks the same as the nominative.

Here rower is the direct object of zostawiły, so it is in the accusative case. But rower is a masculine inanimate noun, and in the singular its accusative usually equals its nominative.

So:

• nominative: rower
• accusative: rower

That is why there is no visible change.

Because the preposition obok requires the genitive case.

The basic form is:

• ławka = bench

After obok, it becomes:

• ławki

So:

• obok ławki = next to the bench

This is worth memorizing: obok + genitive.

Yes, in a purely grammatical sense, ławki is the genitive singular form of ławka. But after a preposition like obok, you should not translate it word-for-word as of the bench. The whole phrase obok ławki simply means next to the bench.

This is very common in Polish: the case ending is required by the preposition, but the natural English translation is a normal location phrase.

Because Polish does not have articles like English a/an and the.

So rower can mean:

• a bicycle
• the bicycle

And ławki in context can mean:

• a bench
• the bench

The exact meaning comes from context, not from an article.

Yes. Polish word order is much more flexible than English word order because case endings show what each word is doing.

This sentence begins with Na podwórku to set the scene first: In the yard...

You could also say things like:

• Dzieci zostawiły rower na podwórku obok ławki.
• Rower dzieci zostawiły na podwórku obok ławki.

These versions are all grammatical, but they place emphasis differently. The original sentence sounds natural and starts with the location, which is often a very normal Polish choice.