The discriminant $\Delta := \Delta(\alpha_1,\,\alpha_2,\,\ldots,\,\alpha_s)$ , of the set $\{\alpha_1,\,\alpha_2,\,\ldots,\,\alpha_s\}$ , of integers of an algebraic number field $K$ is a rational integer. If this set is an integral basis of $K$ then $|\Delta|$ has the least possible (positive integer) value in the field $K$ and conversely. The value $d = \Delta$ , is equal for all integral bases of $K$ and it is called the discriminant or fundamental number of the field.