ENThe discovery and publication of Suprasl Chronicle started the development of studies on the language, context and the circumstances of coming into existencethe West Ruthenian Chronicles ofthe 15th and 16th centuries. It allowed to reveal interesting characteristics of the historiography of Belarus and Lithuania of this period. The development of chronicle writing of the Grand Duchy of Lithuania was divided into stages. Initially, separate historiography narratives were created – chronicles, which were later combined with each other and compilations were created. With time they were supplemented with new pieces of writing as the needs developed, it resulted in subsequentfuller digests. Each of the three digests of ByelorussianLithuanian chronicles is distinguished by its own individuality, connected not only with specific ideological significance, different in particular monuments, but also with the environment it was created in. It was also reflected in the specific linguistic nature of Old Byelorussian chronicles. The purpose of this work was linguistic characteristics of Suprasl Chronicle with regard to phonetic features, changes within declension and verbal flexion, as well as lexical borrowings. The linguistic analysis of the monument text proved that a portion of phonetic and inflection phenomena displays the West Ruthenian realization. Concurrently, the monument shows strong connections with Russian Orthodox traditions, what is reflected on both the phonetic and morphological level. The frequency of particular phonetic phenomena is on a varied level due to that fact most of them did not obtain the position of written standards. On the one hand, it is easy to notice, within lexical borrowings, the influence of the Polish language which mediated to transfer some borrowings into the West Ruthenian language.On the other hand, the text of the chronicle is riddled with Old Slavonic vocabulary what provides subsequent evidence that it has a connection to a literary tradition. A vast majority of phonetic phenomena displays fluctuations between Church Slavonic and (West) Ruthenian realizations. This refers, inter alia, to: 1) realization of ProtoSlavic groups of sounds *tort, *tolt, *tert, *telt, and onset clusters *ort, *olt; 2) onset forms with [o-] collateral to [ie-] (<*ie-); 3) fluctuations of the Church Slavonic realization and Ruthenian realization of clusters *kt’, *gt’, *tj and *dj; 4) records with ки, ги, хи collateral to кы, гы, хы. A strong link to the chronicle writing tradition is attested by a negligible amount of records documenting the transition [e]>[o] after old palatal consonants [ž’], [š’], [č’], [c’] as well as after [r’]. The forms realizing the East Slavonic pattern gain advantage over the Church Slavonic forms, what can be observed in: 1) the development of ProtoSlavic combinations with short close vowels (yers) before consonants [l] and [r]; 2) continuants of the ProtoSlavic groups realization: labial + [j].This monument documents, almost without any exceptions, the vocalisation of short close vowels typical of the Old East Slavic language in the ProtoSlavic combinations *trъt, *tlъt, *trьt, *tlьt. A group of phenomena justified in the West Ruthenian phonetics, without any consequences in the realization, is presented by: 1) spirant change [g]>[h], in Cyrillic monuments realized graphically in the form of кг and к in the place of etymological [g] and the omission of fricative-glottal [h] in words like: осподарь; 2) transition [ł]>[ṷ] in masculine of the past tense; 3) change [u]>[ṷ]; 4) writing ѣ or е in the place of etymological [ě], proving their articulation similarities.5) narrowing of the articulation of [ě] typical of SouthByelorussian and NorthUkrainian dialects; 6) articulation of [a] sound in the place of [o] sound, documented by records with a in the place of etymological [o] in unstressed syllables, and indirectly, some records with o in the place of etymological [a] in an unstressed position; 7) articulation of [e] sound in the place of [’a] sound, strengthened by writing [e] sound in the place of unstressed [’a]. In the monument there are no evident examples confirming the influence of the Polish phonetics. The realization of vowels reduced in the morphemes of words raises conclusions that they were used intuitively, arising from their loss of phonological meaning. The analysis of inflectional forms of nouns, pronouns, adjectives, participles and verbs led to the conclusion that in the field of declension and verbal flexion this chronicle does not substantially differ from the state represented by most of the Old Byelorussian monuments of the 16th century. In the noun inflection there is a noticeable tendency to reduce the number of paradigms with regard to the general Ruthenian system by their unification. Concurrently, the noun inflection system is characterised by fluctuations in endings and inflexional stems, it leads to the occurrence of many collateral forms within particular paradigms. From all types of declension the most permanent turned out to be the declension of *ā. The processes of equalization of declination form into *ŭ are characterized by ǒ-stem declination in gen., dat., loc. singular and plural. Noun forms of consonant declination with *s were almost completely equalized to ǒ-stem declination. Some forms declined into *jǒ, *n, *jā, *ū and *r. were generalized and turned into inflectional endings of declination into *ǐ. [...]. [From the publication]