I lived in Belarus for some time, and my wife is from there. We spoke only Russian while in the country, but most signs, public transportation announcements ("next stop", etc.) and documents were in the Belarusian language.
I've learned very basic amounts of Belarusian, and I'm wondering what the linguistic similarity (language family, etc) is between it and the Russian language. It seems to me to be more mutually understandable with Polish, but it has quite a few "Russian-sounding" words as well as a seemingly similar grammatical structure.
Also, sorry, for some reason it's not letting me "@" your name at the beginning of my comments.
– galois Dec 15 '14 at 16:35@Johnin comment to John’s answer, he will get notification even without it. ⁂ As for your question, you should also note, that Bielorussian and Ukrainian have quite a lot of words loaned from Polish (and most of them were by turn borrowed from German). You may encounter them even among the most everyday vocabulary. E. g. biel. дзякуй ‘thanks’ ← pol. dzięk ← mid.-low-germ. dank. – Dmitry Alexandrov Dec 15 '14 at 18:53