Definition of the concept of a “complex system” in the context of sustainable development science

The article analyzes the main provisions in relation to complex systems. The systems that are studied in the framework of the science of sustainable development are considered. The relationship of the concept of a complex system with the concept of a system is described in detail, as well as the requirements for the system in the context of the study are analyzed. Based on material from various sources, the requirements for the concept of a complex system in the context of research in the field of sustainable development are proposed. The requirements for a complex system have been formed. The complexity criteria are described in detail and such a system is defined in the context of the study.