This paper aims to investigate the role and status of sonority in the development of Bulgarian language. For this purpose, the author explains the concept of sonority, sonority hierarchy of vowels and consonants in the beginning of main discourse. And then analyzes common Slavic(CS), old Bulgarian(OCS) and contemporary Bulgarian and russian linguistic data. The results of this study can be summarize as follows. (1) For the rising sonority in the syllable was introduced open syllable structure during the end of CS and beginning of OCS. Every syllable was ended by vowels in that time. (2) Palatalization, investigated during the end of CS and beginning of OCS, also helped this rising sonority phenomenon. In this article, this phenomenon was analyzed by the sonority hierarchy(8 grades), proposed by Jespersen, 1926 (For exam. * bogъ ＞ bož'e, * gělŏ ＞ zělъ). (3) Contemporary Bulgarian is a language with higher sonority than other slavic languages(Specially than russian). This phenomenon is caused by Bulgarian 6 vowel system(5 in russian), productive use of post definite article(а, то, та, те) and relatively rare soft consonant in the syllable(about 50% less than russian). мгла(R) - мъгла(Bg), мстить(R) - мъстя(Bg), акр(R) - акър(Bg) столът, масата, селото, градовете

This paper aims to investigate the role and status of sonority in the development of Bulgarian language. For this purpose, the author explains the concept of sonority, sonority hierarchy of vowels and consonants in the beginning of main discourse. And then analyzes common Slavic(CS), old Bulgarian(OCS) and contemporary Bulgarian and russian linguistic data. The results of this study can be summarize as follows. (1) For the rising sonority in the syllable was introduced open syllable structure during the end of CS and beginning of OCS. Every syllable was ended by vowels in that time. (2) Palatalization, investigated during the end of CS and beginning of OCS, also helped this rising sonority phenomenon. In this article, this phenomenon was analyzed by the sonority hierarchy(8 grades), proposed by Jespersen, 1926 (For exam. * bogъ ＞ bož'e, * gělŏ ＞ zělъ). (3) Contemporary Bulgarian is a language with higher sonority than other slavic languages(Specially than russian). This phenomenon is caused by Bulgarian 6 vowel system(5 in russian), productive use of post definite article(а, то, та, те) and relatively rare soft consonant in the syllable(about 50% less than russian). мгла(R) - мъгла(Bg), мстить(R) - мъстя(Bg), акр(R) - акър(Bg) столът, масата, селото, градовете

Bulgarian Language, Sonority, Hierarchy, Open Syllable, Palatalization, Phonetics.