My (polish :]) parents gave me a few polish books and to thank them, I said "Dziękuję dla książek" and they corrected me by saying "Dziękuję za książki". Why is 'za' used as 'for' here?
"Za" has quite numerous meanings. Let's see some of them:
za (+ instrumental) behind (denotes location) -> Za domem jest basen (Behind the house there's a swimming pool)
za (+ accusative) behind (denotes movement) -> Poszliśmy za dom (We went behind the house)
za (+ accusative) after/in a (?) (something will happen after a certain period of time) --> za minutę/za godzinę/za miesiąc (in a minute/hour/month)
za (+ accusative) in, for -> I don't know what about this 'in', but this has to be your example: Dziękuję za książki (Thank you for the books); Nienawidzę cię za to co zrobiłeś (I hate you for what you've done), etc.
And then there's "[Serdecznie] dziękuję za uwagę" at the end of a presentation. [Heartfelt] thanks for (your) attention.
Not really, it changes the sentence too much. You start your sentence with the pool, some already known pool. In the Polish sentence you know that there's some house, but the pool is a new piece of information.
Is basen accusative or nominative? The drop down menu says accusative but I thought the pool was the subject, hence nominative.
here it is nominative. but basen is masculine not animated so accusative the same as nominative. Unfortunately Polish nouns have often one "version" for more than one case, and not all cases show in the drop down menu.
On the webside you just place mouse pointer over the word, on the Android app, you have a sentence to translate you touch the word.
In this instance can 'za domem' also be translated as 'in back of the house'? To my ear, 'in back of the house' and 'behind the house' mean the same thing.
i translated as 'behind the house there is a pool' which was counted as wrong.
What's wrong with "behind home there is a swimming pool". In English you do not use articles that often.