Types of Relations in Maths with Examples and Properties
The concept of relations and its types plays a key role in mathematics and is widely applicable to both real-life situations and exam scenarios. Understanding relations helps us describe and analyze how elements from one set are connected to elements from another set. It is one of the foundations of set theory, discrete mathematics, and builds strong reasoning skills for higher studies.
What Is Relations and Its Types?
A relation in Maths is a rule or association that shows the connection between elements of one set (say, A) and elements of another set (B). These connections are represented using ordered pairs. The different types of relations include empty relation, universal relation, identity relation, inverse relation, reflexive, symmetric, transitive, and equivalence relation. You’ll find this concept applied in areas such as set theory, functions, computer science, and logical reasoning.
Key Formula for Relations and Its Types
Here’s the standard way to represent a relation:
If A and B are two sets, then a relation R from A to B is a subset of the Cartesian product A × B.
\( R \subseteq A \times B \)
Why Are Relations Important?
Relations describe how two or more objects are connected or interact. They are a stepping stone to understanding functions, mapping rules, and even database management in computer science. In everyday life, relations help explain: “Who is related to whom?” (family trees), or “Which cities are connected by flights?”
Types of Relations in Maths
There are several types of relations in maths based on the way elements of sets connect. Each type has special properties that are important for board exams and competitive exams.
| Relation Type | Definition | Identifier Tip |
|---|---|---|
| Empty Relation | No element of the set is related to any element (including itself). | R = ∅ or ∅ |
| Universal Relation | Every element of the set is related to every element (including itself). | R = A × A |
| Identity Relation | Every element is related only to itself. | R = { (a,a) | a ∈ A } |
| Inverse Relation | Each ordered pair is reversed. | If (a,b) ∈ R, then (b,a) ∈ R⁻¹ |
| Reflexive Relation | Every element is related to itself (may have others too). | All (a,a) ∈ R |
| Symmetric Relation | If (a,b) ∈ R, then (b,a) ∈ R. | Test (a,b) → (b,a) |
| Transitive Relation | If (a,b) ∈ R and (b,c) ∈ R, then (a,c) ∈ R. | Test chain: (a,b), (b,c) → (a,c) |
| Equivalence Relation | Reflexive + symmetric + transitive together. | All three hold |
| Antisymmetric Relation | If both (a,b) and (b,a) ∈ R, then a = b. | (a ≠ b) ⇒ only one occurs |
Examples of Relations and Their Representation
Ordered Pair: If A = {1, 2, 3}, B = {2, 3}, then a relation R can be: R = { (1,2), (2,3) }.
Representation methods:
- Roster form: List all ordered pairs explicitly.
- Set-builder form: { (x, y) | x ∈ A, y ∈ B, y = x + 1 }
- Arrow diagram: Draw arrows from A to B for each pair in R.
How to Determine Relation Types (Step-by-Step)
- Reflexive: Check if for every a ∈ A, (a,a) ∈ R.
- Symmetric: For every (a,b) ∈ R, verify (b,a) ∈ R.
- Transitive: For (a,b), (b,c) ∈ R, ensure (a,c) ∈ R.
- Check for antisymmetric, identity, and others by their definition.
Solved Example: Exam-Style Problem
Given: A = {1, 2, 3}, R = { (1,1), (2,2), (3,3), (1,2), (2,1) }
Is R reflexive, symmetric, transitive?
1. Reflexive: All (a,a) ∈ R for a ∈ A? Yes (1,1), (2,2), (3,3) are present.2. Symmetric: (1,2) ∈ R and (2,1) ∈ R; for any pair (a,b) in R, (b,a) is also in R. Yes.
3. Transitive: (1,2) ∈ R and (2,1) ∈ R; is (1,1) ∈ R? Yes. Repeat check for all.
Conclusion: R is reflexive, symmetric, and transitive → equivalence relation.
Try These Yourself
- Define a relation R on the set A = {2, 4, 6} such that a divides b. List all ordered pairs of R.
- Check if the relation {(1,1), (2,2), (1,2)} on A = {1,2} is reflexive.
- Is the relation "is the mother of" symmetric?
- Which relation type suits the statement: “a and b have the same birthday”?
Frequent Errors and Misunderstandings
- Missing one or more (a,a) pairs in reflexive relation checks.
- Confusing symmetric with transitive property.
- Thinking all relations are functions (not true!).
- Forgetting that “universal” and “empty” relations are two extremes (all or none).
Relation to Other Concepts
The idea of relations connects closely with Types of Sets and difference between Relation and Function. Mastering relations will make learning about functions and equivalence relations much easier in higher classes.
Classroom Tip
A quick way to remember reflexive, symmetric, and transitive is “Self–Flip–Chain.” That is, reflexive = self, symmetric = flip order, transitive = chain together. Vedantu’s teachers simplify these with visuals and worksheets in their live sessions.
Wrapping It All Up
We explored relations and its types—from definition, table of types, formulas, examples, and error traps. Keep practicing relation problems and reviewing key connection rules. Check Vedantu for more solved examples and practice material to boost your confidence in this chapter.
