quotient group

《代数学引论》 · 第 39 页 · 定义 7

$G/H$ 在陪集的乘法下所成的群称为 $G$ 对正规子群 $H$ 的商群。

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《Algebra》 · 第 42 页 · Chapter I，Section 5「Normality, Quotient Groups, and Homomorphisms」，Theorem 5.4 及其后定名段

Theorem 5.4. If $N$ is a normal subgroup of a group $G$ and $G/N$ is the set of all (left) cosets of $N$ in $G$, then $G/N$ is a group of order $[G:N]$ under the binary operation given by $(aN)(bN)=abN$. […] If $N$ is a normal subgroup of a group $G$, then the group $G/N$, as in Theorem 5.4, is called the quotient group or factor group of $G$ by $N$.