Old Czech

The Czech language developed at the close of the 1st millennium from common West Slavic. Until the early 20th century, it was known as Bohemian. Early West Slavic Among the innovations in common West Slavic is the palatalization of velarch > š (vьšь 'all'), while s (vьsь) developed in the East and South Slavic dialects. Within West Slavic, Czech and Slovak separated from Polish around the 10th to 12th centuries. Some other changes took place during roughly the 10th century: the disappearance and vocalization of yers according to Havlík’s Yer Law (bъzъ > bez, bъza > bza (gen.), later bezu 'elder, lilac');the contraction of groups vowel + j + vowel (dobriji > dobr’í, dobroje > dobré 'good');the denasalization of nasalę [ẽ] > ä and ǫ [õ] > u.The disappearance of the odd yers strengthened the phonological contrast of palatalized (softened) and unpalatalized consonants, and resulted in alterations of epenthetic e and ∅ (null-phoneme). The contrast of the vowel quantity (length) was also strengthened. The depalatalization of consonants preceding e and ä took place later, thus the frequency of occurrence of palatalized consonants was lowered, but it strengthened t