how is it classified?
Czech is distinguished from other West Slavic languages by a more-restricted distinction between "hard" and "soft" consonants
Czech language
Czech is a member of the West Slavic sub-branch of the Slavic branch of the Indo-European language family. This branch includes Polish, Kashubian, Upper and Lower Sorbian and Slovak. Slovak is the most closely related language to Czech, followed by Polish and Silesian.

The West Slavic languages are spoken in Central Europe. Czech is distinguished from other West Slavic languages by a more-restricted distinction between "hard" and "soft" consonants (see Phonology below).
what is the main language in czech republic Czech
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Czech language [SEP] Classification
Czech is a member of the West Slavic sub-branch of the Slavic branch of the Indo-European language family. This branch includes Polish, Kashubian, Upper and Lower Sorbian and Slovak. Slovak is the most closely related language to Czech, followed by Polish and Silesian. The West Slavic languages are spoken in Central Europe. Czech is distinguished from other West Slavic languages by a more-restricted distinction between "hard" and "soft" consonants (see Phonology below).