N-ary associativity
In algebra, -ary associativity is a generalization of the associative law to -ary operations.
A ternary operation is ternary associative if one has always
that is, the operation gives the same result when any three adjacent elements are bracketed inside a sequence of five operands.
Similarly, an -ary operation is -ary associative if bracketing any adjacent elements in a sequence of operands do not change the result.