Formation (group theory)

In group theory, "formation" refers to a class of groups that share certain properties, particularly related to their behavior with respect to subgroup structure, normal subgroups, and composition factors. Formations are typically defined in the context of specific conditions that a group must satisfy to belong to the formation. The most common way to define a formation is through the concept of a **variety** of groups (a class of groups defined by a set of group identities) that is closed under certain operations.