**Identity Relation : **

The rule for identity relation is given below.

**"Every element is related to itself only"**

Let R be a relation defined on the set A

If R is identity relation, then

R = {(a, a) / for all a ∈ A}

That is, every element of A has to be related to itself only.

In case, there is an ordered pair (a, b) in R, then R is not identity. Because the ordered pair (a, b) does not satisfy the above rule of identity relation.

**Example 1 :**

Let A = {1, 2, 3} and R be a relation defined on set A as

R = {(1, 1), (2, 2), (3, 3)}

Verify R is identity.

**Solution : **

In the set A, we find three elements. They are 1, 2 and 3.

When we look at the ordered pairs of R, we find the following associations.

(1, 1) -----> 1 is related to 1

(2, 2) -----> 2 is related to 2

(3, 3) -----> 3 is related to 3

In R, every element of A is related to itself and not to any other different element.

That is, every element of A is related to itself only.

So, R is identity.

**Example 2 :**

Let A = {1, 2, 3} and R be a relation defined on set A as

R = {(1, 1), (2, 2), (3, 3), (2, 3)}

Verify R is identity.

**Solution : **

In the set A, we find three elements. They are 1, 2 and 3.

When we look at the ordered pairs of R, we find the following associations.

(1, 1) -----> 1 is related to 1

(2, 2) -----> 2 is related to 2

(3, 3) -----> 3 is related to 3

(2, 3) -----> 2 is related to 3

In R, every element of A is related to itself and also the element "2" is related to a different element "3".

Here, we can not say that every element of A is related to itself only.

So, R is not identity.

The two relations reflexive and identity appear, as if they were same.

But, there is a huge difference between them.

The difference between reflexive and identity relation can be described in simple words as given below.

**Reflexive : Every element is related to itself**

**Identity : Every element is related to itself only**

Let us consider an example to understand the difference between the two relations reflexive and identity.

Let A = {1, 2, 3}.

Let R_{1} and R_{2} be two relations defined on set A such that

R_{1} = {(1,1), (2,2), (3,3), (1,2)}

R_{2} = {(1,1), (2,2), (3,3)}

When we look at **R _{1}**, every element of A is related to itself and also, the element "1" is related to a different element "2".

**More details about R _{1} :**

(i) "1" is related to "1", "2" is related to "2" and "3" is related to "3"

(ii) Apart from "1" is related to "1", "1" is also related to "2"

Here we can not say that "1" is related to "1" only.

Because "1" is related to "2" also.

This is the point which makes the reflexive relation to be different from identity relation.

**Hence R _{1} is reflexive relation.**

When we look at **R _{2}**, every element of A is related to it self and no element of A is related to any different element other than the same element.

**More details about R _{2} :**

(i) "1" is related to "1", "2" is related to "2" and "3" is related to "3"

(ii) "1" is related to "1" and it is not related to any different element.

The same thing happened to "2" and "3".

(iii) From the second point, it is very clear that every element of R is related to itself only. No element is related to any different element

This is the point which makes identity relation to be different from reflexive relation.

**Hence ****R _{2}** is identity relation.

That is,

**Reflexive : Every element is related to itself**

**Identity : Every element is related to itself only**

**Difference between reflexive and identity relation**

After having gone through the stuff given above, we hope that the students would have understood identity relation.

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