A collection of objects is called a set. The number of elements in every set leads to their classification into different types. Therefore, you can say a set is a collection of dissimilar elements of the same kind. The following are the types of sets:-
A set with only one element present is called a singleton set. For example, Set Y = (4) is a singleton set.
When the set is empty, or it doesn’t have any elements, it is called a null or void set. It is represented by {} or ϕ.
For example A = (x:x is a leap year between 2000 and 2004)
Between 2000 and 2004, we cannot find any leap year so, A = ϕ
When a set consisting of some elements from the original is considered a proper subset; when a set contains original elements, along with the null set, it is called an improper subset.
When in a set, the number of elements is finite, it is called a finite set. All the empty sets come under this category. In other words, a collection of no, or a constant number of elements is known as a finite set. For example:
C= ( x : x in a month in a year); Set C will have 12 elements.
D = (y : y is the zero of a polynomial (x4 – 6x2 + x + 2)); Set D will have 4 zeroes.
It is just the opposite of a finite set. When in a set, the number of elements is infinite, it is called an infinite set. For example:
D = (x : x is a natural number); There are infinite natural numbers. Thus, Set D is an infinite set.
E = (y : y is the ordinate of a point on a given line); Here, you can see there are infinite points on a line. So, E is an infinite set.
Every set is formed based on the universal set and, as per the context, the Universal set is ascertained. Subsets of Universal sets are all the other sets, represented by U.
For example:-
The universal set of integers, rational numbers, and irrational numbers is the set of real numbers.
Two sets C and D will be equal only when each element of set C is also the element of the set D. Even if they are subsets of each other, they will be called equal. It can be illustrated, as:
C = D
C ⊂ D and D ⊂ C ⟺ C = D
If the condition is not met, which is mentioned above, the sets will be considered unequal. It can be shown as C ≠ D.