associative

Concise Oxford English Dictionary © 2008 Oxford University Press:
associative/əˈsəʊʃiətɪv/

▶adjective

• 1 of or involving association.

• 2 Mathematics involving the condition that a group of quantities connected by operators gives the same result in whichever order the operations are performed, as long as the order of the quantities remains the same, e.g. (a × b) × c = a × (b × c).