The result when two things are added together.

The result when two things are subtracted from each other.

Involving the condition that a group of quantities connected by operations gived the same result whatever the order of te quantities involved e.g. 2 x 3 = 3 x 2

Involving the condition that a group of quantities connected by operations gives the same results whatever the grouping, i.e. in whichever order the operations are performed, as long as the order of the quantities remains the same. E.g. (2 x 3) x 4 = 2 x (3 x 4)