This study presents the experience of calculating the differential features of substantive word forms that explicate in speech different degrees of functional and functional-semantic convergence with the class of adverbs of interval. Using the example of the instrumental case form poroj (sometimes), the combinatorics and proportion of features of nuclear and peripheral nouns, as well as nuclear substantive adverbs, that explicate different stages of adverbialization in typical contexts, are demonstrated. The application of oppositional analysis in the study of different conditions for the use of the instrumental case form made it possible to identify the main stages of its adverbialization – the starting and final points of transposition, as well as the zone of peripheral nouns. The absence of intermediate (hybrid) structures and peripheral, functional proper adverbs in the transition zone between the nuclear noun and the nuclear adverb is substantiated. The dynamics of semantic and grammatical features of the substantive word form poroj (sometimes) are analyzed in different contexts in modern Russian language. The adverbial transposition of the word form under consideration is established to have a functional and semantic character. It is associated with the loss of semantic and grammatical features of a noun and the acquisition of categorical properties of adverbs, as well as with violation of the semantic identity of the original substantive lexeme and the formation of not only a grammatical, but also a lexical homonym, which is included in the subclass of adverbs of an interval exceeding a certain situational norm. The conclusion is relevant for the general theory of transitivity and syncretism in the field of semantics and grammar.