n. The act of alternating, or the state of being alternate; the reciprocal succession of things in time or place, or of states or actions; the act of following something and being in turn followed by it: as, the alternation of day and night, cold and heat, summer and winter.n. Passage back and forth; repeated transition; the action of going from one state, condition, or point to another, and back again, indefinitely: as, alternation between states of mind or between places; his alternations from one point to the other were very frequent.n. In mathematics: The different changes or alterations of order in numbers. More commonly called permutation.n. Alternate proportion (which see, under alternate, a.).n. 4. In church ritual, the saying or reading of parts of a service by minister and congregation alternately.n. In phytogeography, the discontinuous occurrence of a plant type due to local variations in the conditions. See the extract.n. In electricity, the time of one reversal, or one half-wave of alternating current. One alternation therefore is one half-cycle. The frequency of an alternating current formerly was given in alternations per minute. See alternating.