# NCERT Class 11 Mathematics/Sets – Chapter 1

**NCERT Class 11 Mathematics/Sets – Chapter 1 is about the important points to be studied about Sets. Here you can find out the important definitions of sets and different types of sets.**

**NCERT Class 11 Mathematics/SETS – Chapter 1Important Points to Remember:**

*Set*: A set is a well-defined collection of objects.

There are two methods of representing a set:

i) *Roster or tabular formii) Set-builder form*

In roster form, the order in which the elements are listed is immaterial.

While writing the set in roster form an element is not generally repeated.

*The Empty Set or the Null Set or the Void Set:*

A set which does not contain any element is called the empty set or the null set or the void set.

*Finite and Infinite Sets:*

A set which is empty or consists of a definite number of elements is called finite otherwise, the set is called infinite.

*Equal Sets:*Two sets A and B are said to be equal if they have exactly the same elements and we write A=B.

Otherwise, the sets are said to be unequal.

A set does not change if one or more elements of the set are repeated.

*Subsets:*A set A is said to be a subset of a set B if every element of A is also an element of B.

*Power set:*The collection of all subsets of a set A is called the power set of A. It is denoted by P (A).

*Union of sets:*

The union of two sets A and B is the set C which consists of all those elements which are either in A or in B (including those which are in both).

*Intersection of sets:*

The intersection of two sets A and B is the set of all those elements which belong to both A and B.

*Difference of sets:*

The difference of the sets A and B in this order is the set of elements which belong to A but not to B. Symbolically, we write A – B.

*Complement of a set:*

Let U be the universal set and A a subset of U. Then the complement of A is the set of all elements of U which are not the elements of A.