alternation

(countable, uncountable) 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
(countable, uncountable) The response of the congregation speaking alternately with the minister.
(countable, uncountable) Ablaut.
(countable, uncountable) A pattern by which more than one construct is possible, as with "Alice cooked Bob dinner" and "Alice cooked dinner for Bob".
(countable, uncountable) The "inclusive or" truth function.
(countable, uncountable) A sequence that alternates between positive and negative values.
(countable, proscribed, uncountable) A permutation.
(countable, uncountable) A construct in a regular expression that can match any of several specified subexpressions.
(countable, uncountable) A type of partial truncation of a polygon, polyhedron or tiling in which alternate vertices are removed.