Successive change from one thing or state to another and back again.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "alternation" in a sentence
"A NI posting has been, in recent years, a doddle for most squaddies, especially when the alternative, the alternation is a spell in Basra or Helmand."
"The tract is direct psalmody — the singing of successive verses of a psalm without refrain, and it is sung in alternation by two halves of the choir."
"Credit Suisse had said it expected around 200-300 orders to be announced this year at Farnborough, held every other year in alternation with the Paris show."