The study of high-frequency and low-frequency language means is of interest from the point of view of the development and preservation of the richness and variability of the language. The object of the study is complex sentences with subordinate clauses of condition, cause, purpose, concessions, consequence, combined into a common group of sentences with the meaning of conditionality. The research is based on materials of scientific and journalistic styles, which are rich in topic and scope of users. Analysis of various examples of real language use makes it possible to determine which structural models of these sentences are the most common, core, and which belong to the periphery, and what causes such variability. The study of language means of forming complex sentences includes the use of conjunctions as the main structural elements of expressing the meaning of conditionality, the order of predicative parts, as well as the modal-tense characteristics of predicates. Stabe, core structural means of the sentences under consideration have been identified, which ensure the stability of the language system. Unproductive means serve to express specific kinds of condition, cause, purpose, concession meanings and come under peripheral variants characteristic of the styles under consideration. Differences in the use of linguistic means in forming complex sentences of these types have stylistic, semantic, and communicative reasons.