Czech, Polish, Slovak - Are These West Slavic Languages Pretty Much the Same?

So, if the grammar is already similar in the wider Slavic group, you can imagine that the more closely related West Slavs have even more to share. Since the differences within vocabulary come down to different historic influences, the Czech-Slovak language which is already closely related, also shares so much of vocabulary as to be mutually intelligible to a high degree. In many ways, it is impossible to distinguish between these two. Most of the differences come more down to regional dialects than an easily distinguishable distinction between the languages.