takahmamash:
The difference between a language and a dialect is largely political. In recent times such languages as Ukranian and Afrikaans (not to mention Serbian, Croatian and Bosnian) were declared by local governments. The day before they were all regional dialects. The act of parliament declaring the local regional dialect to be a “language” has nothing to do with whether people could understand each other. As most Jews could only read the Hebrew alphabet, they were unware whether the person they were speaking a slavic language to was writing it in Roman or Cyrillic (and indeed, until recently, the person they were speaking with was probably illiterate).