The geometric mean is a number, which is used to represent a set of numbers. It is calculated by taking the n-th root of the product of these numbers. In symbols, if we have numbers , the geometric mean is
Because there's a product, it does not make sense to calculate the geometric mean if one of the numbers is zero. It generally also does not make much sense to calculate it when one of them is a negative number. It isn't used for complex numbers, because calculating the root of a complex number has more than one result.