Direct product (sets)
If $A_i:i=1,2, \ldots, n$ are sets, their direct product
$$ \begin{equation*} A_1\times A_2 \times \cdots \times A_n=\{(a_1, a_2 \ldots, a_n): a_i \in A_i\}; \end{equation*} $$
If $A_i:i=1,2, \ldots, n$ are sets, their direct product
$$ \begin{equation*} A_1\times A_2 \times \cdots \times A_n=\{(a_1, a_2 \ldots, a_n): a_i \in A_i\}; \end{equation*} $$