Let X = {1, 2, 3, 4, 5, 6} and let T1 = {X, %3D 4, {2}, {1,2}, {2,3,4}, {1, 2,3,4}} and T2 = {X, þ, {2}, {1,2,3}, {4,5,6}, {2,4,5,6}} * T1 and T2 are both not topologies on X T1 is a topology on X and T2 is not a topology on X O 11 and T2 are both topologies on X T1 is not a topology and T2 is a topology on X o O

In simple mathematics terms, a domain is defined as the space on which all the possible inputs for the function will lie. It can also be expressed as a set of departures for the required function.