Ja wolę kawę, a ona woli herbatę.

Because the verb changes depending on the subject.

The dictionary form is woleć = to prefer.

In the present tense:

• ja wolę = I prefer
• ty wolisz = you prefer
• on/ona/ono woli = he/she/it prefers
• my wolimy = we prefer
• wy wolicie = you all prefer
• oni/one wolą = they prefer

So:

• ja wolę matches I
• ona woli matches she

That is true: Polish often omits subject pronouns because the verb ending already shows who the subject is.

So Wolę kawę already means I prefer coffee.

Here, ja is included mainly for emphasis or contrast. The sentence sets up a comparison:

• Ja wolę kawę, a ona woli herbatę.

This feels like:

• I prefer coffee, while she prefers tea.

So ja and ona help make the contrast clearer and stronger.

A often means and, while, or whereas, depending on context.

In this sentence, it is contrastive:

• Ja wolę kawę, a ona woli herbatę.
• I prefer coffee, while she prefers tea.

It connects two ideas and shows a contrast, but usually a milder contrast than ale.

A useful comparison:

• a = and/while/whereas
• ale = but

So here a is the natural choice because the sentence compares two preferences rather than strongly opposing them.

Because they are direct objects, and in Polish direct objects often go in the accusative case.

The verb woleć takes a direct object:

• prefer what? coffee
• prefer what? tea

The base forms are:

• kawa = coffee
• herbata = tea

Their accusative singular forms are:

• kawę
• herbatę

So:

• wolę kawę
• woli herbatę

This is a very common pattern with feminine nouns ending in -a:

• nominative: -a
• accusative: -ę

Examples:

• mam książkę = I have a book
• widzę kobietę = I see a woman
• lubię kawę = I like coffee

Yes. For many feminine singular nouns ending in -a, the accusative ends in -ę.

For example:

• kawa → kawę
• herbata → herbatę
• książka → książkę
• kobieta → kobietę

So this sentence is a good example of a very important Polish pattern.

The basic dictionary form is woleć.

It is best to learn:

1. the infinitive: woleć
2. a few key present-tense forms:
   • wolę
   • wolisz
   • woli
3. what case it requires:
   • usually the accusative for the thing preferred

That way you can build sentences easily:

• Wolę kawę.
• Wolisz herbatę?
• On woli sok.

Yes, Polish word order is more flexible than English word order.

For example, these are possible:

• Ja wolę kawę, a ona woli herbatę.
• Wolę kawę, a ona woli herbatę.
• Kawę wolę, a ona woli herbatę.

But they do not all sound exactly the same in emphasis.

The version you were given is very neutral and clear. It highlights the two subjects:

• ja
• ona

That makes sense because the sentence contrasts my preference with her preference.

You could omit ja, but omitting ona would usually make the second part less clear unless context already tells you the subject.

For example:

• Wolę kawę, a ona woli herbatę. = very natural
• Wolę kawę, a woli herbatę. = usually unclear, because who prefers tea?

So in this sentence, ona is especially useful because the second clause introduces a different subject.

A simple learner-friendly pronunciation guide:

• wolę sounds roughly like VOH-weh with a nasal ending
• woli sounds roughly like VOH-lee
• kawę sounds roughly like KAH-veh with a nasal ending
• herbatę sounds roughly like her-BAH-teh with a nasal ending

About ę:

• It is a nasal vowel in Polish.
• At the end of a word, many speakers pronounce it less strongly nasal than learners expect.
• So in normal speech, final ę may sound somewhere between a nasal vowel and a plain e.

Do not worry if your ę is not perfect at first. What matters most is recognizing that -ę is an important grammatical ending here.

Because Polish verbs must agree with the subject.

• wolę is only for ja = I
• woli is for on / ona / ono = he / she / it

So:

• ja wolę
• ona woli

Using ona wolę would be grammatically wrong, just like saying she prefer in English.

Both can connect contrasting ideas, but they are not used in exactly the same way.

• a often means and, while, or whereas
• ale means but

Compare:

• Ja wolę kawę, a ona woli herbatę.
  • I prefer coffee, while she prefers tea.
• Ja wolę kawę, ale nie mam żadnej.
  • I prefer coffee, but I do not have any.

In your sentence, a sounds natural because it compares two people’s preferences side by side.

It is a very useful general model.

You can reuse the same structure with many nouns:

• Ja wolę sok, a ona woli wodę.
• Ja wolę lato, a ona woli zimę.
• Ja wolę psy, a ona woli koty.

So the sentence teaches several important things at once:

• present tense of woleć
• accusative objects
• contrast with a
• optional but useful subject pronouns for emphasis

Not exactly. They are similar, but not the same.

• lubię = I like
• wolę = I prefer

So:

• Lubię kawę = I like coffee
• Wolę kawę = I prefer coffee

Wolę usually implies a comparison, stated or implied. In your sentence, that comparison is very clear:

• I prefer coffee
• she prefers tea

So wolę is the better choice for expressing preference.