alternation

Short definition from Wiktionary

Noun

1. 1
   The reciprocal succession of (normally two) things in time or place; the act of following and being followed by turns; alternate succession, performance, or occurrence
2. 2
   The response of the congregation speaking alternately with the minister.
3. 3
   Ablaut.
4. 4
   A pattern by which more than one construct is possible, as with "Alice cooked Bob dinner" and "Alice cooked dinner for Bob".
5. 5
   The "inclusive or" truth function.
6. 6
   A sequence that alternates between positive and negative values.
7. 7
   A permutation.
8. 8
   A construct in a regular expression that can match any of several specified subexpressions.
9. 9
   A type of partial truncation of a polygon, polyhedron or tiling in which alternate vertices are removed.