In his dissertation The Division of Labour in Society (1893), Emile Durkheim identifies a behavioral tendency to unite and relate which he deemed "mechanical solidarity".
Mechanical solidarity is the tendency to bond and create a community. Within this community, dynamics such as interdependence (affinity), and unity are the result of common interests, beliefs, and lifestyles.
By "mechanical", Durkheim means "automatic", that is, that there is no direct intervention or alternative agent applied to the process of bonding. People immediately tend to attach themselves, whether psychologically or socially, to others who share their state of mind.
Mechanical solidarity mainly manifests in small communities and traditional settings, for example, the suburbs, where people tend to divide themselves by interests such as sports, church, hobbies, sexual orientation, type of employment, and other social circles.