2-group
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This article is about 2-dimensional higher groups. For p-groups with p = 2, see p-group.
Not to be confused with No. 2 Group RAF.
In mathematics, particularly category theory, a 2-group is a groupoid with a way to multiply objects, making it resemble a group. They are part of a larger hierarchy of n-groups. They were introduced by Hoàng Xuân Sính in the late 1960s under the name gr-categories,[1][2] and they are also known as categorical groups.