The notion of environment, relative to the category of system, includes not only the external environment (surrounding), but also the internal environment (context) of the system. However, the notion of internal environment in the system theories, social and ecological sciences is comprehended ambiguously or is lacking completely. The article provides comparative analysis of various internal environment conceptions as well as its correlation with the system and the external environment and justifies the inconsistency of identifying the internal environment with the composition of elements or with the relationship between the system constituents. The authors suggest their interpretation of the notion "internal environment (context)" as the substance of its elements, properties and relationship as well as the processes taking place outside the control of the system. We consider the content and essence of the notion "context" with regard to the social, natural and socio-natural systems, special peculiar features of the ecology of these systems, its environmental and contextual aspects. The ecology of the social and socio-natural systems external environment includes the relationship between the person and the society with natural and artificial environment and the issues of people's physical health. The state of the internal environment of these systems constitutes the subject of psychic ecologycare about spiritual life and human mental health, preservation of historical and cultural memory of the system, its subjectivity and ability to autopoiesis. The unity of the environmental and contextual approaches in ecology is particularly important amidst the crisis of the global socio-natural system.