Set:
A set is a collection of distinct objects. These distinct objects are called the element of the sets. Sets are denoted by the capital letters. The class of grade 7 is a set of students. Also a room is set of different objects including sofas, chairs, and walls etc as its elements. We use a special symbol to denote that an object is an element of a particular set. If A is a set of fruits then to show that apple is an element of set is represented as, apple Î A. And because spinach cannot be an element of set A we denote it as spinach ÏA. A set is enclosed in brackets.

Examples:
A = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }
B = ( set of alphabets }
C = { Ali , Billy , Anna , Sarah }

Some frequently used sets:
1. N = {1, 2, 3, 4, 5…}
Set of natural numbers.
2. W = {0, 1, 2, 3, 4, 5…}
Set of whole numbers.
3. Z = {…-4, -3, -2, -1, 0, 1, 2, 3, 4…}
Set of integers.
4. Z+ = {0, 1, 2, 3, 4…}
Set of [positive integers.
5. Z- = {-1, -2, -3, -4...}
Set of negative integers.
6. E = {-4, -2, 0, 2, 4…}
Set of even integers.
7. O = {…-5, -3, -1, 1, 2, 3…}
Set of odd integers.

Some special sets:
· Equivalent sets.
· Non equivalent sets.
· Universal sets.
· Empty set.
· Infinite set.
· Finite set.

Equivalent sets:
If the number of elements in a set are equivalent to another set, then they are called equivalent sets.
Example:
A= {24, 25, 26 , 27}
B = {100, 200, 300, 400}
The sets are equivalent.

Non equivalent sets:
If the number of element in a set are not equal to another set then the sets are called non equivalent sets.
Example:
X= {24, 25, 26, 27, 28}
Y = {100, 200, 300, 400}
The sets are non equivalent.

Finite:
If we can count the elements of a set we call it a finite set.
Example:
A = {2, 4, 7, 9}
Here A is a finite set.

Infinite sets:
If we start counting the elements of a set and the process does not come to end, then the set is infinite.
Example:
B = {1, 2, 3, 4, 5,…}
B is an infinite set.

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