The relevance of support for research on the methodology of building information and analytical systems is determined by the separation and justification of basic concepts. In this context, based on view of the relevance of the topic of the article on the results obtained analytically, before proceeding to the practical aspects of building any information-analytical system, given the transdisciplinarity of scientific knowledge, it is always appropriate to conduct structural-logical or semantic analysis terminology. This makes it possible to clarify the essence and content of the basic concepts of research and to outline the vector of further research. It is noted that in the conditions of modern information communications all objects of information-analytical interaction, regardless of their origin, are directly or indirectly interconnected. The purpose of the research is to provide basic categorical-conceptual support for doctoral research on the methodology of building information and analytical systems. In this sense, the methods of content analysis, semantic and comparative analysis, ontological modelling, etc. were used, which allowed identifying several types of approaches to determining the amount of information exchanged by objects in the process of information interaction: algorithmic, entropic, combinatorial, ontological, semantic, synergistic, transdisciplinary and pragmatic. The results and conclusions of the research are in the range of issues that allow us to understand the essence of the definition of «Information-Analytical System»; the semantics of the terms «Information», «Information Object», «Information Environment», «Information Space», «Information-Analytical Interaction», «Semantic Environment», etc.; the special nature of information as such, which distinguishes it from matter and energy, is emphasized; it is noted that information exists only in the presence of its carriers, which have a material and energy form; the relationship between the concepts of «Information Environment», «Information-Analytical Field» and «Information Space» is revealed, which is derived from the content of the basic concept of «Information». The ontological approach as a basic tool of semantic (informational) analysis is studied (within which it is possible to calculate the semantic similarity of semantic interpretations of text tokens in relation to the immediate semantic environment, i.e. context); it is noted that the construction of ontologies is based on the fixation of logical constructions that contain dictionaries of terms of the thematic area and on the description of the definitions of these terms, their theoretically possible and impossible semantic connections; it is noted that the basis for building an ontology can be user requests; the mathematics of the process of ontological modeling is briefly presented. The current definition of «Information-Analytical System» based on the results of semantic analysis is given.