"Piszemy książkę po angielsku."

Translation: We are writing a book in English.

[Tinyset]

Can we say 'We are writing an English book?'

[tadjanow]

I'm not completely sure, but to me 'English book' sounds like a book about English (e.g. a grammar guide) rather than a book written in English.

[fredpareto]

I agree. How would one write 'We are writing an English book' then?

[Emwue]

Assuming it is a book about English, it would be "Piszemy książkę o [języku] angielskim", but I feel most of the times a native speaker(me for sure) would be more specific here, so it would be, for example, "Piszemy książkę o gramatyce angielskiego"(We are writing a book about English grammar), "Piszemy książkę o historii angielskiego(history of English [language]), "[…]o fonologii angielskiego"(English phonology) and so on, depending on the topic.

[wildleoappeared]

That should be correct
It's true that it can have a different meaning but it should be considered a correct translation

[frandogk3]

"An English book" could mean several things, based on context. To be perfectly clear that the book is in English as opposed to someother language, "a book in English" works best.

[JedenPolska]

Does po mean in?

[immery]

only in this context - speaking, writing in a language.

I checked a dictionary http://sjp.pwn.pl/szukaj/po.html po has 19 meanings,

Usually po means after popołudnie= afternoon

[infj98]

Do polish prepositions usually take the nominative then? Or is that not the nominative

[immery]

Prepositions do not change, so they do not have cases.

Words after preposition take different cases depending on preposition and context.

And here in "po ....u" it's not a real case, it's a special word form of adjective just for this kind of expressions.

I did write somewhere a list of possible meanings of po+ adjective, but it's basically- like we they do it there .

[ZeLisou]

Why isn't "we write" a correct answer ?

[JerryMcCarthy99]

But it is.... However, if you made an error somewhere in your typing, then the "correct" answer at the top of Duo's list will be shown, and that happens to be the "we are writing" version.

[PeterJ422616]

since the verb is in the present tense you can also say we write

[malcolm651145]

If the translation says "we are writing a book in english". The translation "we are writing an english book" uses the actice voice and would be an equally good translation which should not be marked incorrectly

[Jellei]

"an English book" is very ambiguous.