1. SETS
A set is a collection of objects of any kind which are collected together perhaps because of some property they have in common.
Examples: The collection of numbers used for counting, the collection of all paintings of an artist.
Mainly the objects of a set are required to be “well defined”.
The objects which make up a set are called its members or elements.
If the number of elements in a set is finite is called as finite set.
Sets having infinitely many elements are called infinite sets.
Set having only one element is called a singleton set.

2. SETS Continued…. For describing a set, two methods are commonly used:
1.The Tabulation Method
2.The Rule Method
In tabulation method, all elements of a set are written down within braces(flower brackets) if there are too many elements ,the first few elements are written down in such a way as to indicate clearly what others are.
In rule method ,we specify the set by stating a characteristic property which all the elements of the set possess and which no other object possesses.
Example: If ‘S’ is the set of all positive odd integers , then S can be described as shown……

3. SETS Continued…. S={1,3,5,7……} S={x/x is a positive odd integer}
The tabulation method is used in the first of above descriptions of S and the rule method is used in the second.
The first description is read as:” S is the set consisting of the elements 1,3,5,7….” and the second description is read as :”S is the set of elements ‘x’ such that ‘x’ is a positive odd integer”. In the second description , the vertical line within the brackets stands for “such that”.
The singleton set consisting of the element a is described by the tabulation method and is denoted by {a}.