Przedsiębiorca wyjaśnia koszt odesłania.

Because some masculine nouns in Polish take the -a ending in the nominative singular. Przedsiębiorca is one of them. It means entrepreneur / business owner, and grammatically it is still masculine.

This pattern is common with nouns referring to people, for example:

• kolega = male friend
• mężczyzna = man
• poeta = poet

So even though the ending may look feminine to an English-speaking learner, przedsiębiorca is masculine.

It is in the nominative singular, because it is the subject of the sentence — the person performing the action.

In Przedsiębiorca wyjaśnia koszt odesłania, the entrepreneur is the one who explains something, so przedsiębiorca must be nominative.

Koszt is the direct object, so it is in the accusative singular. However, for many masculine inanimate nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: koszt
• accusative: koszt

That is why the form does not change.

Compare:

• Widzę stół = I see the table
• Wyjaśnia koszt = He/she explains the cost

In both examples, the masculine inanimate object keeps the same form.

Wyjaśnia is the 3rd person singular present tense form of wyjaśniać, which is an imperfective verb.

It can mean:

• he explains
• she explains
• it explains

Polish usually does not need a separate subject pronoun like he or she, because the verb ending already shows the person and number. Here, the noun przedsiębiorca tells us who is doing the action.

Because here Polish uses a verbal noun, not an infinitive.

• odesłać = to send back
• odesłanie = sending back / return
• odesłania = of sending back / of return

So koszt odesłania literally means something like the cost of sending back or the cost of return shipment.

This is very common in Polish. Instead of using an infinitive after a noun, Polish often uses a noun phrase:

• czas gotowania = cooking time
• koszt naprawy = cost of repair
• możliwość wyjazdu = possibility of leaving

Odesłania is in the genitive singular.

Why? Because it depends on koszt. In Polish, many nouns are followed by another noun in the genitive to express of ....

So:

• koszt odesłania = cost of return / cost of sending back
• cena produktu = price of the product
• koniec dnia = end of the day

This is a very important Polish pattern: noun + genitive noun.

No, Polish word order is fairly flexible, because case endings show grammatical roles.

The neutral order here is:

• Przedsiębiorca wyjaśnia koszt odesłania.

But other orders are possible, for example for emphasis:

• Koszt odesłania wyjaśnia przedsiębiorca.
• Wyjaśnia przedsiębiorca koszt odesłania.

These alternatives may sound more marked or stylistically different, but they are grammatically possible. The original version is the most straightforward and natural as a basic sentence.

A rough pronunciation guide is:

pshet-shyem-BYOR-tsa

A few useful points:

• rz often sounds like zh or sh/zh depending on the context
• się sounds roughly like shyem
• ę is a nasal vowel, but before some consonants it is often pronounced in a simplified way
• stress in Polish is usually on the second-to-last syllable, so here the stress is on -bior-

You do not need to pronounce every letter exactly like in English spelling. It is better to learn the sound pattern gradually.

Because Polish has no articles. There is no direct equivalent of a or the as regular articles like in English.

So przedsiębiorca can mean:

• an entrepreneur
• the entrepreneur

And koszt can mean:

• a cost
• the cost

The exact meaning depends on context.

Yes, it is grammatical, but in real-life usage it may sound a little context-dependent or slightly formal. A Polish speaker might often add more detail, for example:

• Przedsiębiorca wyjaśnia koszt odesłania towaru.
  = The entrepreneur explains the cost of sending the goods back.

• Przedsiębiorca wyjaśnia koszty odesłania.
  = The entrepreneur explains the return costs.

Still, the original sentence is perfectly useful for learning grammar:

• subject: przedsiębiorca
• verb: wyjaśnia
• object: koszt
• genitive dependent noun: odesłania

The dictionary forms are:

• przedsiębiorca = entrepreneur, business owner
• wyjaśniać = to explain
• koszt = cost
• odesłanie = sending back, return
  • related verb: odesłać = to send back

So the sentence is built from very common Polish patterns:

• a nominative subject
• a present-tense verb
• an accusative object
• a genitive noun after another noun