Английский словарь Webster - phase (3)

(n.) The relation at any instant of a periodically varying electric magnitude, as electro-motive force, a current, etc., to its initial value as expressed in factorial parts of the complete cycle. It is usually expressed in angular measure, the cycle beb four right angles, or 360!. Such periodic variations are generally well represented by sine curves; and phase relations are shown by the relative positions of the crests and hollows of such curves. Magnitudes which have the same phase are said to be in phase.