On the question of syntactic synonymy of adverbial and subordinate constructions

This article examines the phenomenon of syntactic synonymy between adverbial constructions, particularly adverbial inflections, and complex sentences with subordinate adverbial parts, such as those expressing time or reason. The authors justify the relevance of the topic by highlighting its connection with improving speech culture, accurately expressing thoughts, and the variability of grammatical means in modern Ukrainian. Particular attention is paid to the formal- grammatical and semantic- functional characteristics of parallel syntactic synonyms. The author analyses the conditions under which constructions can be interchanged without losing the main meaning or grammatical correctness. Examples from literary and folklore texts are considered to demonstrate the temporal, causal, conditional, permissive, and target correlations between the components of the constructions under comparison. The study establishes that the choice between synonymous structures depends on grammatical features, stylistic requirements, semantic accuracy, and the genre‑ specificity of the utterance. The author proves that constructions with adverbs mostly function in written literary style, whereas complex subordinate clauses are more typical of colloquial speech. This study contributes to a deeper understanding of the nature of syntactic synonymy and its future research prospects within functional grammar.