N-ary times operator

Read it as a product over the indicated inputs.

“N-ary” means that an operation takes n inputs; it does not mean raising a number to the nth power. Small labels beside, above or below the operator can specify which inputs to include. The large sign collects the operation into one expression instead of writing a chain of multiplication signs.

When the inputs are sets, this can denote a Cartesian product: the set of ordered choices containing one member from each input set. For example, combining a set of colours with a set of sizes gives colour-and-size pairs. This is a product of sets, rather than ordinary multiplication of numbers.