Denote \(n\)-nary¹ multiplication with “the big pi”

\begin{equation*} \prod_{i = 1}^{n} x_i = x_1 \times x_2 \times \timess \times x_{n - 1} \times x_n, \end{equation*}

or equivalently

\begin{equation*} \prod_{x \in S} x_1 \times x_2 \times \timess \times x_{n - 1} \times x_n \end{equation*}

given the set of terms \(S = \{x_1, x_2, \ldots, x_{n - 1}, x_n\}\).