direct product

《近世代数》 · 第 47 页

综上所述，$G_1\times G_2$ 成为一个群，称它为群 $G_1$ 与 $G_2$ 的直积，仍记做 $G_1\times G_2$。

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《Abstract Algebra》 · 第 17-18 页 · Section 1.1「Basic Axioms and Examples」，Example (6)

If $(A,*)$ and $(B,\diamond)$ are groups, we can form a new group $A\times B$, called their direct product, whose elements are those in the Cartesian product $A\times B=\{(a,b)\mid a\in A,\ b\in B\}$ and whose operation is defined componentwise: $(a_1,b_1)(a_2,b_2)=(a_1*a_2,b_1\diamond b_2)$.