The term group is an amorphous one and can refer to a wide variety of gatherings, from just two people (think about a “group project” in school when you partner with another student), a club, a regular gathering of friends, or people who work together or share a hobby. In short, the term refers to any collection of at least two people who interact with some frequency and who share a sense that their identity is somehow aligned with the group. Of course, every time people are gathered, it is not necessarily a group. A rally is usually a one-time event, for instance, and belonging to a political party doesn’t imply interaction with others. People who happen to be in the same place at the same time but who do not interact or share a sense of identity—such as a bunch of people standing in line at Starbucks—are considered an aggregate, or a crowd. Another example of a nongroup is people who share similar characteristics but are not tied to one another in any way. These people are considered a category, and as an example all children born from approximately 1980–2000 are referred to as “Millennials.” Why are Millennials a category and not a group? Because while some of them may share a sense of identity, they do not, as a whole, interact frequently with each other. Interestingly, people within an aggregate or category can become a group. During disasters, people in a neighborhood (an aggregate) who did not know each other might become friendly and depend on each other at the local shelter. After the disaster when people go back to simply living near each other, the feeling of cohesiveness may last since they have all shared an experience. They might remain a group, practicing emergency readiness, coordinating supplies for next time, or taking turns caring for neighbors who need extra help. Similarly, there may be many groups within a single category. Consider teachers, for example. Within this category, groups may exist like teachers’ unions, teachers who coach, or staff members who are involved with the PTA.