∩: intersection. For example, A∩B represents the set of all elements in set A and set B.

∈: belongs to. For example, a∈A means that element A belongs to set A.

{}: This is the representation of a set. For example, the set A = {1, 7,6} indicates that there are three elements in the set A: 1, 7,6.

∩lieng means that the previous set is contained in the latter set, that is, all elements in the previous set are in the latter set.

∩lie with≠ means that the previous set is contained in the latter set, and the two sets are not equal.