In a seminal 1986 study, McMillan and Chavis identify four elements of "sense of community":
membership,
influence,
integration and fulfillment of needs,
shared emotional connection.
McMillan & Chavis (1986) define sense of community as "a feeling that members have of belonging, a feeling that members matter to one another and to the group, and a shared faith that members' needs will be met through their commitment to be together."
McMillan, D.W., & Chavis, D.M. (1986). Sense of community: A definition and theory. Journal of Community Psychology, 14(1), 6-23.