In a broad sense, it is an accidental or premeditated, private or public, long-term or short-term, verbal or non-verbal personal contact between two or more people, entailing mutual changes in their behavior, activities, attitudes and attitudes. Such an interpretation is usually used to indicate the direct interconnection of individuals who act with each other. In the narrow sense, it is a system of mutually conditioned individual actions connected by a cyclic causal dependence, in which the behavior of each of the participants is both a stimulus and a reaction to the behavior of the others.