A social group is two or more people who interact and share a sense of identity. It is not just a category of people. A crowd waiting for a bus is not a group. A bowling team is. Members interact, influence each other, and feel they belong.

Groups can be small or large, formal or informal. Primary groups are small and intimate. Secondary groups are larger and impersonal. In-groups are those we belong to. Out-groups are those we do not. Reference groups are those we compare ourselves to, even if we do not belong.

Types of groups

• Primary: family, close friends
• Secondary: coworkers, classmates
• In-group: us
• Out-group: them
• Reference group: a standard for comparison

Groups shape behavior. People act differently in groups than alone. They conform, compete, cooperate, and sometimes do terrible things they would never do alone. The group is a fundamental unit of social life.