@Dušan what makes polish grammatically more eastern? Grammatically polish is fully western slavic with several anomolies even grammatically I would think Slovak is closer to Russian. Just the way Polish forms words like Cos or Ktos is strange instead of niečo or niekto as in most other slavic languages. Slovak imo isnt even a fully western slavic language like polish and czech but filled south slavic and east slavic characteristics. both czech and slovak say Co for what while slovak is more like the other slavic branches with čo and some central slovak dialects used to use the world čto.
lexical relationship between slavic languages. It confirms what I thought. Lower number equals less distance between the languages lexically. @NikeBG take a look how close bulgarian is lexically to Russian compared to other east slavic languages!