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Automorphism group of a group
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This article is about a basic definition in group theory.The article text may, however, contain advanced material.
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Definition
Symbol-free definition
The automorphism group of a group is defined as a group whose elements are all the automorphisms of the base group, and where the group operation is composition of automorphisms. In other words, it gets a group structure as a subgroup of the group of all permutations of the group.
Definition with symbols
The automorphism group of a group G, denoted Aut(G), is a set whose elements are automorphisms 
, and where the group multiplication is composition of automorphisms. In other words, its group structure is obtained as a subgroup of Sym(G), the group of all permutations on G.
Subgroups
Every group-closed automorphism property gives rise to a normal subgroup of the automorphism group. Examples are the property of being an inner automorphism, class automorphism, extensible automorphism.
