"Znam sławnego pisarza."

Translation: I know a famous writer.

[MmeLVaillancourt]

Would pisarza not also be : author?

[Emwue]

Well, author is pretty synonymous to writer, so outside Duo for sure(though author has a broader meaning and can be used for creator of any kind of art, not just writing). As for Duo course, generally there is tendency for very literal translations, so since author="autor" and writer="pisarz" it might be not accepted – still, I would report it on your place, maybe it is just an oversight?

[hughcparker]

Author usually means writer of books. Writer could also mean journalist or advertising copywriter, etc.

[Emwue]

The meanings aren't 100% the same between Polish and English language, so in short, no, not really.

Pisarz:

PWN

1. «ten, kto pisze, zwłaszcza prozą, utwory literackie»
2. «w dawnych urzędach miejskich, kancelariach królewskich itp.: urzędnik pełniący funkcję sekretarza»

WSJP

• autor utworów literackich
• w dawnych urzędach i kancelariach: urzędnik, który wykonywał obowiązki sekretarza i czuwał nad sprawami administracyjno-prawno-finansowymi

Autor:

PWN

1. «twórca dzieła literackiego lub naukowego, też: dzieła sztuki, wynalazku, projektu itp.»
2. «inicjator jakiegoś przedsięwzięcia»
3. «wykonawca jakiejś czynności»

WSJP

• osoba, która stworzyła jakieś dzieło
• osoba, która wymyśliła i zapoczątkowała jakieś działania
• osoba, która wykonała jakąś czynność

So, although „autor” is a hypernym of „pisarz”(in Polish language, at least), when referring to an author of literary works, they are synonyms. Also, a journalist is simply „dziennikarz” in Polish; copywriter is either „copywriter” or sometimes „tekściarz”.

[arminia11_web_de]

sław, słab...I know a weak writer. Gah. Too many words look alike in Polish!

[Popo-lsku]

My question is... What is the different between "popular" and "famous"? I know, there are some other words for popular like "popularny" but is it not possible to mix it up in this case?

[Jellei]

Well, you can be a popular person at school, but it doesn't mean that you're famous, as no one apart from your family, friends and people at school knows you. So we want to stick to that.

[Popo-lsku]

Thank you very much. Now i understand! :)

[Tim62192]

Why is it Pisarza? This is the accusative (I think!) so the noun should not change ... or is this an exception like "Pies" -> "Psa"?

[Jellei]

It's not an exception. It is Accusative, true, but only some nouns do not change in Accusative.

Accusative is identical to Nominative for: neuter singular, 'not masculine-personal' plural and masculine singular inanimate.

So it was "I know this film", the Polish word "film" is masculine, but inanimate, so it wouldn't change. But both "pies" from your example and "pisarz" are animate nouns, and for those, the Accusative form is identical to Genitive (not sure if you already learned Genitive), not to Nominative.

[Tim62192]

Aaaaah! Thank you! Now I understand why we have 'kota' and 'konia' in the Accusative :)