Peripheral subgroup

In group theory, a branch of abstract algebra, a **peripheral subgroup** is a specific type of subgroup that has particular significance in the study of group actions and the structure of groups. A subgroup \( H \) of a group \( G \) is called a *peripheral subgroup* if it meets certain criteria within the context of a relatively small subgroup of \( G \) that is critical to the structure of \( G \).