associative property
noun [ U ] mathematics specialized uk/əˌsəʊ.si.ə.tiv ˈprɒp.ə.ti/ us/əˌsoʊ.si.ə.tiv ˈprɑː.pɚ.t̬i/
（数学的）结合性，结合原则
the mathematical principle that the order in which three numbers are grouped when being added or multiplied does not matter