The Collaborative International Dictionary of English v.0.48:

Alternation \Al`ter*na"tion\, n. [L. alternatio: cf. F.
   alternation.]
   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.
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   2. (Math.) Permutation.
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   3. The response of the congregation speaking alternately with
      the minister. --Mason.
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   Alternation of generation. See under Generation.
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