Havlík's law

'''Havlík's law''' is a Slavic rhythmic law dealing with the reduced vowels (known as yers or jers) in Proto-Slavic. It is named for the Czech scholar Antonín Havlík (1855–1925), who determined the pattern in 1889. While Havlík's law was a precursor to the loss of the yers, that process is part of the individual history of the various Slavic languages. Havlík's law was already in effect at the end of the Common Slavic period, and ended the era of the "law of open syllables", a major phonological innovation of the Common Slavic period. Provided by Wikipedia