a group can be defined as two or more humans who interact with one another, accept expectations and obligations as members of the group, and share a common identity. By this definition, society can be viewed as a large group, though most social groups are considerably smaller. A true group exhibits some degree of social cohesion and is more than a simple collection or aggregate of individuals, such as people waiting at a bus stop. Characteristics shared by members of a group may include interests, values, ethnic or social background, and/or kinship ties. According to Hare, the defining characteristic of a group is social interaction.

Group dynamics is a system of behaviors and psychological processes occurring within a social group (intragroup dynamics), or between social groups (intergroup dynamics). The study of group dynamics can be useful in understanding decision-making behaviour, tracking the spread of diseases in society, creating effective therapy techniques, and following