A crowd waiting for a train is not a group. Neither is everyone in a country who is left-handed. Sociologists call the first an aggregate, people in the same place at the same time, and the second a category, people who share a trait. A social group is different: two or more people who interact, share a sense of belonging and have some common identity. Groups are where most of social life actually happens.

Primary and secondary groups

Cooley, whose looking-glass self appeared in the last level, also distinguished two kinds of groups in Social Organization (1909). A primary group is a small, close group valued for its own sake, such as a family or a circle of close friends. Members know one another as whole people, and the relationship is its own reward. Secondary groups are larger and more impersonal, formed to reach a goal: a work team, a class, a professional association. Most people move between both all day, and many secondary groups contain primary groups within them, as when coworkers become close friends.

People also compare themselves with groups they do not belong to. A reference group is a group whose standards people use to judge themselves. A law student may measure success against successful lawyers, not against fellow students. Choosing a different reference group can change how satisfied a person feels, even when nothing else in their life has changed.

Why size matters

The German sociologist Georg Simmel noticed that the number of members changes a group's character. A dyad, a group of two, is intimate but fragile: if either person leaves, the group ends. Adding one person creates a triad, and with it new possibilities. A triad can survive one member leaving and allows a third party to mediate disputes. It also allows coalitions, two against one. As groups grow, intimacy fades, and formal rules and leaders tend to appear.

The strength of weak ties

Groups link into larger networks, and the shape of a network matters. In a 1973 paper the American sociologist Mark Granovetter argued that weak ties, connections to acquaintances, are often more useful than strong ones for certain purposes. In a study of how people found jobs, he found that many heard about openings through people they saw only occasionally. The reason is that acquaintances move in different circles and so bring new information. Close friends tend to know the same people and hear the same news you do.

Bureaucracy

Modern life is full of formal organizations: companies, hospitals, universities, government agencies. Weber described their typical form, the bureaucracy, as an ideal type, a model that highlights key features. It has a clear hierarchy, a division of labor, hiring by qualifications, careful records and written rules applied impersonally to every case. Weber saw real advantages here. Impersonal rules can be fairer than rule by personal favor, and bureaucracy is efficient at large tasks.

He and later scholars also saw costs. One is goal displacement: rules becoming ends in themselves rather than means to a goal, so that a clerk follows procedure even when it defeats the purpose of the office. The German Italian sociologist Robert Michels, studying socialist parties that preached democracy, proposed an iron law of oligarchy in 1911: large organizations tend to end up run by a small elite. Leaders control information and resources, and members lack the time to watch them closely. In 1993 the American sociologist George Ritzer described McDonaldization: the spread of fast-food principles of efficiency, predictability and control to more and more of society, from schools to medicine.

Institutions

Above organizations are social institutions: lasting patterns of norms, roles and organizations that meet basic social needs. The family, education, religion, the economy, government and health care are the classic examples. An institution is not one building. Education includes millions of schools, the laws that govern them and the shared expectations about what a student or a teacher should do. The levels that follow look at several of these institutions in turn.

Worked example: a refugee family settles in

Amira and her two children arrive as refugees in a city where they know almost no one. Their primary group, the family itself, gives emotional support but little practical knowledge of the new country. At first Amira's reference group is the life she left; she measures every day against what was lost. A caseworker connects her to a refugee association, a secondary group, and through it she meets dozens of acquaintances. One of them, a woman she has spoken to only twice, mentions a clinic hiring interpreters. That weak tie, not any close friend, leads to Amira's first job.

Meanwhile the family navigates bureaucracies: housing, schools and benefits offices. Impersonal rules protect them from officials who might dislike foreigners, but the same rules sometimes demand documents they lost in flight. A good caseworker knows when to follow procedure and when to fight goal displacement. Seeing the family's situation through these concepts shows where help can come from, and where systems built for efficiency forget that every case file is a person.