Solidarity

According to Wikipedia, Solidarity is the integration shown by a society or group with people and their neighbors. It refers to the ties in a society that bind people to one another. The term is generally employed in sociology and the other social sciences.

What forms the basis of solidarity varies between societies. In simple societies it may be mainly based around kinship and shared values. In more complex societies there are various theories as to what contributes the sense of social solidarity...

According to Émile Durkheim, the types of social solidarity correlate with types of society. Durkheim introduced the terms "mechanical" and "organic solidarity" as part of his theory of the development of societies. In a society exhibiting mechanical solidarity, its cohesion and integration comes from the homogeneity of individuals—people feel connected through similar work, educational and religious training, and lifestyle. Mechanical solidarity normally operates in "traditional" and small scale societies. In simpler societies (e.g., tribal), solidarity is usually based on kinship ties of familial networks. Organic solidarity occurs in "modern" and "industrial" societies. It is social cohesion based upon the dependence individuals in more advanced societies have on each other. Although individuals perform different tasks and often have different values and interests, the order and very solidarity of society depends on their reliance on each other to perform their specified tasks. Organic here refers to the interdependence of the component parts. Thus, social solidarity is maintained in more complex societies through the interdependence of its component parts (e.g., farmers produce the food to feed the factory workers who produce the tractors that allow the farmer to produce the food).
See the table comparing mechanical and organic solidarity

For other definitions of solidarity see Miriam Webster or dictionary.com