Pertaining to, resulting from, or characterised by association; capable of associating; tending to associate or unite.

(algebra, of a binary operator ∗ {\displaystyle *} ) Such that, for any operands a , b {\displaystyle a,b} and c {\displaystyle c} , ( a ∗ b ) ∗ c = a ∗ ( b ∗ c ) {\displaystyle (a*b)*c=a*(b*c)} ; (of a ring, etc.) whose multiplication operation is associative.

(computing) Addressable by a key more complex than an integer index.