Morele są dziś tańsze niż wczoraj, więc kupuję je na deser i na poranną przekąskę.

Morele is the plural form of morela, meaning apricot.

So:

• morela = one apricot
• morele = apricots

In this sentence, the speaker is talking about multiple apricots.

Polish does not have articles like English the, a, or some.

So morele can mean things like:

• apricots
• the apricots
• some apricots

The exact meaning depends on context. That is completely normal in Polish.

Są is the 3rd person plural present form of być, meaning to be.

So:

• morele są tańsze = the apricots are cheaper

In Polish, when you say that something is a certain way using an adjective, you normally keep the verb być in the present tense. So unlike in some other Slavic languages, Polish does not usually drop it here.

Because the adjective has to agree with morele.

Morele is plural, and in the plural it takes the non-masculine-personal adjective form. That is why the comparative is tańsze.

Here is the pattern:

• tani = cheap
• tańszy / tańsza / tańsze = cheaper

In this sentence:

• morele
  • tańsze = correct agreement

Yes. Niż means than, and wczoraj means yesterday.

So:

• tańsze niż wczoraj = cheaper than yesterday

More fully, the idea is:

• cheaper than they were yesterday

Polish often leaves out words that are understood from context, just like English does in sentences such as Prices are lower today than yesterday.

Dziś means today.

Yes, you can also say dzisiaj. Both are very common and usually interchangeable.

So these are both natural:

• Morele są dziś tańsze
• Morele są dzisiaj tańsze

Dziś is just the shorter form.

Więc means so, therefore, or as a result.

It connects the two parts of the sentence:

• The apricots are cheaper today than yesterday, so I’m buying them...

It shows that the second action is the result of the first fact.

Because Polish usually leaves out subject pronouns when the verb ending already shows who is doing the action.

Kupuję means I buy / I’m buying, and the ending -ę already tells you it is I.

So:

• kupuję = I buy / I’m buying
• ja kupuję = I buy / I’m buying, but with extra emphasis

You would add ja only if you wanted contrast or emphasis.

Because kupuję is the imperfective present form, while kupię is perfective future.

• kupuję = I am buying / I buy
• kupię = I will buy

In this sentence, kupuję presents the purchase as a current action or immediate decision. It sounds like: They’re cheaper today, so I’m buying them.

If you said kupię, it would sound more like so I will buy them.

Je means them here. It replaces morele so the speaker does not have to repeat the noun.

So:

• kupuję je = I’m buying them
• kupuję morele = I’m buying apricots

Both are possible. Je is simply the direct object pronoun.

Here it refers back to morele, which are plural and non-masculine-personal.

Not if you still want the object clearly stated in this exact sentence.

• kupuję je = I’m buying them
• kupuję = I’m buying

If you remove je, the sentence no longer explicitly says what is being bought. Polish can omit objects when context makes them obvious, but here je is useful because it clearly points back to morele.

In Polish, na + accusative often expresses purpose or intended use.

So:

• na deser = for dessert
• na poranną przekąskę = for a morning snack

The speaker is saying what the apricots are intended for.

Because after na in this meaning, Polish uses the accusative.

The base forms are:

• przekąska = snack
• poranna = morning

In the accusative singular feminine, they become:

• przekąskę
• poranną

They match each other because the adjective must agree with the noun.

Repeating the preposition is very natural in Polish and often sounds clearer.

So:

• na deser i na poranną przekąskę = very natural
• na deser i poranną przekąskę = possible in some contexts, but less clear or less balanced here

Repeating na makes it obvious that both phrases are separate purpose phrases.

No, Polish word order is fairly flexible.

For example, you could also say:

• Dziś morele są tańsze niż wczoraj...
• Morele dziś są tańsze niż wczoraj...

These all mean roughly the same thing, but the emphasis changes slightly.

The original sentence is very natural and neutral: Morele są dziś tańsze niż wczoraj, więc kupuję je na deser i na poranną przekąskę.