symmetric group

《代数学引论》 · 第 28 页

当 $M$ 含有 $n$ 个元素时，$M$ 的可逆变换称为 $n$ 元置换，$S(M)$ 称为 $n$ 元对称群，简记为 $S_n$。

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《Abstract Algebra》 · 第 29 页 · Section 1.3「Symmetric Groups」

Let $\Omega$ be any nonempty set and let $S_\Omega$ be the set of all bijections from $\Omega$ to itself (i.e., the set of all permutations of $\Omega$). The set $S_\Omega$ is a group under function composition: $\circ$. […] This group is called the symmetric group on the set $\Omega$.