"The hen is drinking water."
Translation:Η κότα πίνει νερό.
Unfortunately ύδωρ is not used in modern Greek, it's found only in compound words like υδροηλεκτρική ενέργεια - hydroelectric power. If someone used it, it would seem like they had traveled forward in time and their Greek is not up to date! :)
Κότα is the best translation. Are you sure that the article you used was η and not το, or ο?
The strange thing is it said, you used the wrong word: and it corrected Kota (sorry only my phone has the greek letters) and gave the longer word, which almost looks like in English it would be henbird, lol --but what I did was type the word Kota that it gives in the dropdown "hint" from clicking on the underlined word for hen. That's why I was surprised it was wrong.
Yes, I'm afraid that you probably used the wrong article. That's how Duolingo works. If you use the wrong article, it actually marks the noun wrong, if there is an alternative translation with the article you chose. In this case, το κοτόπουλο (which translates to chicken. :P)
Make sure to always check your article's gender. ^.^