Definition:  number k in the expression $\vartheta}_{0}2\pi \frac{\left(i1\right)k}{m$ for the initial phase of quantity number i of the set of m quantities forming a symmetric polyphase system, where ${\vartheta}_{0}$ is the initial phase of one of the quantities which is arbitrarily chosen out of the set of m quantities, i is one of the integers 1, 2, ..., m, and k is a characteristic of the system, equal to one of the integers 0, 1, 2, ..., m − 1
