Object of Study: Lviv and Moscow editions of Apostol (years 1574 and 1564), as well as distinctions in stress accentuation of nouns, pronouns, adjectives, numerals, adverbs, verbs, and past participles compared to the stress accentuation of the same words in the Proto-Slavonic, Church Slavonic, and Old Ruthenian languages (16-17 centuries). Study Purposes: to investigate stress accentuation distinctions between the content words found in Lviv edition of Apostol (1574) versus Moscow edition (1564), and define stress accentuation peculiarities of the Old Ruthenian language of the 16-17 centuries. Study Methods: descriptive method was applied to discover accentuation distinctions and their parameters within grammatical classes (parts of speech); comparative-historical method, namely method of internal reconstruction, was applied to determine primary Proto-Slavonic accentuation of the analyzed lexical items and their allologs; comparative method was applied to define distinctions of the analyzed words within the morphemic structure; method of quantitative estimation as an element of statistical analysis was applied to define quantity of the accentuation distinctions within each part of speech. Scientific Novelty: first time ever determination, classification, and analysis of accentuation distinctions in the first printed East-Slavonic memorials. In the process of comparative analysis of the lexical items and allologs that had distinctions in Apostol, dictionaries, grammar books, and memorials of the 14 - 18 centuries, it was discovered that the majority of words illustrate Old Ruthenian accentuation of the above mentioned period, distinctive from the Old Russian one. Practical Utility: the results of the study can be applied to compile a dictionary of the Old Ruthenian accentuation; to compile manuals, guide books, and monographs on accentuation; there was developed a dedicated method of analysis of accentuation distinctions in the texts of similar content, which assists in analysis of stress accentuation evolution of a studied word belonging to the Late Proto-Slavonic period; factual material may be applied within a course of History of the Ukrainian Language, specialty courses and specialty seminars on Historical Accentuation in the Ukrainian language, Comparative-Historical Accentuation of the East-Slavonic Languages.
