Types of set

Types of set

There are many types of set in the set theory:

1. Singleton set
If a set contains only one element it is called to be a singleton set.
Hence the set given by {1}, {0}, {a} are all consisting of only one element and therefore are singleton sets.
2. Finite Set
A set consisting of a natural number of objects, i.e. in which number element is finite is said to be a finite set. Consider the sets
A = { 5, 7, 9, 11} and B = { 4 , 8 , 16, 32, 64, 128}
Obviously, A, B contain a finite number of elements, i.e. 4 objects in A and 6 in B. Thus they are finite sets.
3. Infinite set
If the number of elements in a set is finite, the set is said to be an infinite set.
Thus the set of all natural number is given by N = { 1, 2, 3, ...} is an infinite set. Similarly the set of all rational number between ) and 1 given by
A = {x:x E Q, 0 <x<1} is an infinite set.
4. Equal set
Two set A and B consisting of the same elements are said to be equal sets. In other words, if an element of the set A sets the set A and B are called equal i.e. A = B.
5. Null set/ empty set
A null set or an empty set is a valid set with no member.
A = { } / phie cardinality of A is 0.
There is two popular representation either empty curly braces { } or a special symbol phie. This A is a set which has null set inside it.
6. Subset
A subset A is said to be subset of B if every elements which belongs to A also belongs to B.

    A = { 1, 2, 3}
    B = { 1, 2, 3, 4}
    A subset of B.

7. Proper set
A set is said to be a proper subset of B if A is a subset of B, A is not equal to B or A is a subset of B but B contains at least one element which does not belong to A.
8. Improper set
Set A is called an improper subset of B if and Only if A = B. Every set is an improper subset of itself.
9. Power set
Power set of a set is defined as a set of every possible subset. If the cardinality of A is n than Cardinality of power set is 2^n as every element has two options either to belong to a subset or not.
10. Universal set
Any set which is a superset of all the sets under consideration is said to be universal set and is either denoted by omega or S or U.

    Let  A = {1, 2, 3}
    C = { 0, 1} then we can take
    S = {0, 1, 2, 3, 4, 5, 6, 7, 8}