Basic Concepts of Sets

1. Sets

A set is a collection of well-defined objects. 

some example of sets:

• The members of Indian Parliament.
• The set of natural numbers. 
• The set of points on a line, etc.

The objects belonging to a set are called the elements or members of the set.

Sets are usually denoted by capital letters 

Ex. A,B,C,D,.........X,Y,Z,....etc.

and the elements of a set are generally denoted by small letters a,b,c,d,.....,x,y,z...etc.

1.2 Finite and Infinite Sets

A set consisting of finite number of elements i.e., a set whose elements can be put in one-to one correspondence with the subset of natural numbers ciz. {1,2,3,....n,..} for some n, is called a finite set. A set consisting of an infinite number of elemnts i.e, a set which is not finite, is called infinite set.

Ex. X={1,3,5,7,9} is a finite set.

                          The set consisting of all people living in the state of bihar is a finite set.

1.3 singleton set

A set consisting of one element x only is called a singleton set and is denoted by {x}.