The paper interprets the Russian explanatory sentence as a semantic type. It is noted that descriptions of the semantic types of monopropositional sentences have already been carried out in the linguistic literature. For the first time, it is proposed to consider polypropositional semantic structures as a semantic type. The semantic nature of an explanatory sentence is defined as an expression of reflection on the events and phenomena of reality, with the position of the object-event accompanied by an indication of the reflection nature expressed by the governing predicate. General characteristics of this semantic type are given, as well as a number of semantic features serving as the basis for revealing the patterns of compatibility of various types of modus and dictum and the ways of their connection. It is proved that the previously existing qualification of relevance/factuality is based on overestimating the role of the brace and underestimating the predicative expression of deliberative. Several techniques are proposed to distinguish between thematic and factual utterances. Among sentence elements, the concept of the subject is the most significant for the typology of explanatory sentences, proposed to be divided into mono-subject and poly-subject ones. We note the poly-paradigmatic nature of the explanatory sentence and the presence of a number of its transformations used in the texts. The range of explanatory sentences with such an interpretation expands significantly without taking into account the boundaries of simple and complex sentences and some other constructive differences.