Intersection of Sets
The intersection of two given sets is the set that contains all the elements that are common to both sets. The symbol for the intersection of sets is "∩''. For any two sets A and B, the intersection, A ∩ B (read as A intersection B) lists all the elements that are present in both sets. For example, if Set A = {1,2,3,4,5} and Set B = {3,4,6,8}, A ∩ B = {3,4}
What is Intersection of Sets?
In set theory, for any two sets A and B, the intersection is defined as the set of all the elements in set A that are also present in set B. We use the symbol '∩' that denotes 'intersection of'. For example, let us represent the students who like ice creams for dessert, Brandon, Sophie, Luke, and Jessy. This is set A. The students who like brownies for dessert are Ron, Sophie, Mia, and Luke. This is set B. The students who like both ice creams and brownies are Sophie and Luke. This is represented as A ∩ B.
Cardinal Number
The cardinal number of a set is the total number of elements present in the set. For example, if Set A = {1,2,3,4}, then the cardinal number (represented as n (A)) = 4. Consider two sets A and B. A = {2,4, 5, 6, 10, 11, 14, 21}, B = {1, 2, 3, 5, 7, 8,11,12,13} and A ∩ B = {2, 5, 11} where n(A ∩ B) = 3.
n(A ∩ B)= n(A) + n(B)  n(A ∪ B)
Disjoint Sets
Two sets A and B having no elements in common are said to be disjoint, if A ∩ B = ϕ, then A and B are called disjoint sets. Example: If A = { 2, 3, 5, 9} and B = {1, 4, 6,12}, A ∩ B = { 2, 3, 5, 9} ∩ {1, 4, 6,12} = ϕ. Therefore, A and B are called disjoint sets.
Subsets
If a set A is the set of natural numbers from 1 to 10 and set B is the set of odd numbers from 1 to 10, then B is the subset of A. The intersection of sets is a subset of each set forming the intersection, (A ∩ B) ⊂ A and (A ∩ B) ⊂ B.
For example A = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} , B = {2, 4, 7, 12, 14} , A ∩ B = {2, 4, 7}. Thus A ∩ B is a subset of A, and A ∩ B is a subset of B.
Complement of Intersection of Sets
The set of all the elements in the universal set but not in A ∩ B is the complement of the intersection of sets. If X = {1, 2, 3, 4, 5}, Y = {2,4,6,8,10}, and U = {1,2,3,4,5,6,7,8,9,10}, then X ∩ Y = {2,4} and (X ∩ Y)' = {1,3, 5,6,7,8,9,10}. the complement of intersection of sets is denoted as (A∩B)´.
Intersection of Sets Venn Diagram
Venn Diagrams are diagrams used to represent or explain the relationship between set operations. Venn diagrams use circles to represent each set. Overlapping circles denote that there is some relationship between two or more sets, whereas circles that do not overlap do not share any common elements. The following diagram shows the intersection of sets using a Venn diagram. Here, Set A = {1,2,3,4,5} and Set B = {3,4,6,8}. Therefore A ∩ B = {3,4}
Properties of Intersection of Sets
As we have properties for numbers, intersection of sets also have some important properties. The following table lists the properties of the intersection of sets.
Name of Property/Law  Rule 
Commutative Law  A ∩ B = B ∩ A 
Associative Law  (A ∩ B) ∩ C = A ∩ (B ∩ C) 
Law of ϕ and U  ϕ ∩ A = ϕ , U ∩ A= A 
Idempotent Law  (A ∩ (B ∪ C) = (A ∩ B) ∪ (A ∩ C) (A ∪ (B ∩ C) = (A ∪ B) ∩ (A ∪ C) 
Important Notes:
 (A ∩ B) is the set of all the elements that are common to both sets A and B.
 If A ∩ B = ϕ, then A and B are called disjoint sets.
 n(A ∩ B) = n(A) + n(B)  n(A ∪ B)
Topics Related to Intersection of Sets
Check out some interesting articles related to the intersection of sets.
Challenging Questions:
Try to solve these challenging questions related to the topic intersection of sets in math!
 In a group of 100 persons, 85 take tea, 20 take coffee, and 20 neither take tea nor coffee. Find the number of persons who take both tea and coffee.
 Find the intersection of sets between the sets of odd natural numbers and even natural numbers.
Solved Examples

Example 1: If Set A = {a,b,c,d,e,f,g,h,i} and Set B = {a,e,i,o,u}. Find n(A ∩ B).
Solution:
A ∩ B = {a, e, i}
Therefore, n(A ∩ B) = 3. 
Example 2: Let P = {1, 2, 3, 5, 7, 11}, Q = {first five even natural numbers}. Find P ∩ Q and n(P ∩ Q).
Solution:Given P = {1, 2, 3, 5, 7, 11} and Q = {2, 4, 6, 8, 10}.
P ∩ Q = {2}
n(P ∩ Q)= 1
Therefore, P ∩ Q = {2} and n(P ∩ Q)= 1.

Example 3: Given that A = {1,3,5,7,9}, B = {0,5,10,15}, and U= {0,1,3,5,7,9,10,11,15,20}. Find A ∩ B and A ∩ B'.
Solution:A ∩ B = {5}
A ∩ B’ = {0,1,3,7,9,10,11,15,20}
Therefore, A ∩ B = {5} and (A ∩ B)’ = {0,1,3,7,9,10,11,15,20}
FAQs on Intersection of Sets
What is Intersection of Sets?
For any two sets A and B, A ∩ B is defined as the group of elements in set A that are also present in set B. This is known as the intersection of sets.
What does A ∩ B mean in math?
A ∩ B means the common elements that belong to both set A and set B. In math, ∩ is the symbol to denote intersection.
What is Union and Intersection of Sets?
For any two sets A and B, the union of sets, which is denoted by A U B, is the set of all the elements present in set A and the set of elements present in set B or both. The intersection of two sets is the set of elements that are common to both sets A and B.
What Does ∩ Mean in Probability?
If there are two events A and B, then ∩ denotes the probability of intersection of the events A and B.
What is Venn Diagram?
A Venn diagram pictorially represents the relationship between two or more sets.
What is Cardinal Number in a Set?
The total number of elements in a set is called the cardinal number of the set.