utc this periodization of proto slavic ps is not generally accepted however most scholars agree that the ps period lasted for years or so it is impossible that the language would not have been changing for so long that is why reconstructed forms labelled proto slavic are very various indeed supnas supnu sunu and s n 'a dream' or 'sleeping' can all be termed proto slavic there is not even the agreement when the period ended some give even ad as the final date after which individual languages existed others say that ocs ca ad was still a literary form of the latest proto slavic of course with strong dialectal local features and there do not seem to be any real basics for any periodization of ps specialists argue even on relative chronology of some language phenomena inc phonetic changes for example some would see the sequence as us u u i e first changing and losing of s next vowel reduction while others would assume as us s i e first vowel reduction then loss of final consonants and to say nothing of the absolute chronology the situation is even more complicated when we took into consideration that most of the literature on the subject is not english and the authors use terms which are not strict renderings for english proto slavic and common slavic in fact in slavic languages there exists the term praslavyanski or silmilar where pra means the same as great in great grandfather praded or similar this term should be translated as old slavic then besides the term protoslavyanski proto slavic refers at least in some sources to the early period of the slavic language commonwealth less or more equal to schenker's eps and finally the russian term obshcheslavyanski 'common slavic' polish og lnos owia ski with the same meaning refers to features which are present in each modern slavic language rather than to their common ancestor anyway i see no reasons for keeping two different articles one on proto slavic the other for common slavic whatever these terms mean august