The article deals with the problem of constructing a definition of the category of intellectual capital. It is concluded that nature of existing definitions of intellectual capital is the contradictory and fragmented. In order to solve this problem, methods of formal logic used in conjunction with the use of tools categorical system methodology and theory of dynamic information systems. The necessary and sufficient signs of this phenomenon, which enable its precise identification, are allocated. Two-tier triadic decryption of the phenomenon of intellectual capital is made. It will result in a definition that meets the requirements of unambiguously distinguishing it from similar groups, but not identical categories.