APA Dictionary of Psychology

the complete set of social relationships among members of a society or other group, which determines the structure of the group and the place of individuals within it. These relationships can be based on several variables: kinship, age, sex, area of residence, and—in human beings—religion, matrimony, or common interests. The social organization is usually implemented by rules of behavior produced by social interactions involving dominance, territoriality, the mating system, and cooperation.