Alternation

n.	1.	The reciprocal succession of things in time or place; the act of following and being followed by turns; alternate succession, performance, or occurrence; as, the alternation of day and night, cold and heat, summer and winter, hope and fear.
	2.	(Math.) Permutation.
	3.	The response of the congregation speaking alternately with the minister. Alternation of generation See under Generation.

Noun	1.	alternation - being regularly exchangeable
	2.	alternation - successive change from one thing or state to another and back again

Lissajous figure, back-and-forth, battledore and shuttlecock, beat, chain, coaction, coming and going, commutation, complementary distribution, concurrence, consecution, cooperation, counterchange, cross fire, cyclicalness, ebb and flow, engagement, exchange, fluctuation, flux and reflux, give-and-take, interaction, interchange, intercommunication, intercourse, interlacing, intermeshing, intermittence, intermittency, intermutation, interplay, intertwining, interweaving, interworking, lex talionis, measure for measure, mesh, meshing, meter, mutual admiration, mutual support, mutual transfer, mutuality, order, oscillation, pendulation, pendulum motion, periodicalness, periodicity, permutation, piston motion, progression, pulsation, quid pro quo, reappearance, reciprocality, reciprocation, reciprocity, recurrence, regular wave motion, reoccurrence, repetition, retaliation, return, reversion, rhythm, rhythmic play, rotation, row, seasonality, seesaw, seesawing, sequel, sequence, series, shifting, shuffling, sine wave, something for something, succession, teeter, teeter-totter, teeter-tottering, teetering, tit for tat, to-and-fro, tottering, train, transposal, transposition, undulation, ups and downs, vacillation, variation, vicissitude, wavering, wigwag