Symmetry – Definition with Examples

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Symmetry

In mathematics, especially in geometry and its applications, an object is said to have symmetry if it can be divided into two identical halves. For example, look at the given picture of a flower:

Flower to describe Symmetry - SplashLearn

If we were to draw an imaginary line in the middle of it, we could divide it into two equal parts like this:

Symmetry Flower - SplashLearn

Note that the two parts are identical and mirror images of each other.

An object that is not symmetric is said to be asymmetric. That means that an asymmetric object cannot be divided into identical halves. 

An example of asymmetry would be the given image.

Asymmetric Object - SplashLearn


Line of Symmetry

The Line of Symmetry - SplashLearn

Let’s look at this flower again, the dotted line along which we divided it into two identical halves is called the line of symmetry or the axis of symmetry. It can also be defined as the line along which we can fold the object and its left and right half would completely overlap with each other. 

In mathematics, there are three types of lines of symmetry. 

  • The Vertical Line of Symmetry
  • The Horizontal Line of Symmetry
  • The Diagonal Line of Symmetry

Let’s take a look at each of these lines.

Vertical Line of Symmetry

A vertical line that divides an object into two identical halves is called a vertical line of symmetry. That means that the vertical line goes from top to bottom (or vice versa) in an object and divides it into its mirror halves. For example, the star below shows a vertical line of symmetry.

Verticsl Line of Symmetry - SplashLearn


The Horizontal Line of Symmetry

When a horizontal line divides an object into two identical halves, it is called a horizontal line of symmetry. That means the horizontal line of symmetry goes from left to right (or vice versa) in an object. For example, the image below shows a horizontal line of symmetry.

Horizontal Line of Symmetry - SplashLearn


The Diagonal Line of Symmetry

When a diagonal/skew line divides an object into two identical halves, it is called a diagonal line of symmetry. For example, the square below shows a diagonal line of symmetry.

Diagonal Line of Symmetry - SplashLearn

In fact, a square possesses all three lines of symmetry.

Square possesses all the line of Symmetry - SplashLearn

So we can say that an object can have multiple lines of symmetry. Some other examples of shapes that have multiple lines of symmetry are circles and rectangles. 

An example of a shape that does not have any line of symmetry is a scalene triangle. Since all sides of a scalene triangle are different, it cannot be divided into two identical mirror halves.

Scalene Triangle - SplashLearn


Symmetry in Real Life 

Symmetry was taught to humans by nature itself. A lot of flowers and most of the animals are symmetric in nature. Inspired by this, humans learned to build their architecture with symmetric aspects that made buildings balanced and proportionate in their foundation, like the pyramids of Egypt! We can observe symmetry around us in many forms:

  • Trees reflected in crystal clear water and towering mountains reflected in a lake.
  • The feathers of a peacock and the wings of butterflies and dragonflies have identical left and right sides.
  • Hives of honeybees are made of hexagonal shape, which is symmetric in nature.
  • Snowflakes in winter have all three lines of symmetry.

Solved Examples

Example 1: How many lines of symmetry does the given figure have?

Symmetry Line Example - SplashLearn

Answer: Only one line of symmetry.

One line of Symmetry - SplashLearn

Example 2: Can you find any examples of letters from the alphabet that have a horizontal line of symmetry?

Answer: A lot of letters, like O, D, H, have horizontal lines of symmetry.

Example 3: Is the given shape symmetric or asymmetric?

Vertical Line of Symmetry - SplashLearn

Answer: The given shape is symmetric with a vertical line of symmetry.

Practice Problems

Symmetry

Attend this Quiz & Test your knowledge.

1How many lines of symmetry does a rectangle have?

2
3
1
4
CorrectIncorrect
Correct answer is: 2
A rectangle has only two lines of symmetry.
Symmetry – Definition with Examples

2Which of the following letters of the alphabet have a horizontal and vertical line of symmetry?

Y
X
P
M
CorrectIncorrect
Correct answer is: X
The letter X has both vertical and horizontal lines of symmetry.

3Which line of symmetry does the following figure have?

Symmetry – Definition with Examples
Horizontal
Diagonal
Vertical
No line of symmetry
CorrectIncorrect
Correct answer is: Vertical
The given figure only has a vertical line of symmetry

4Which of the following numbers has two lines of symmetry?

7
5
3
8
CorrectIncorrect
Correct answer is: 8
The number 8 has two lines of symmetry.

Frequently Asked Questions

Symmetry in math is the property of an object to be able to be divided into two identical mirror halves.

The axis of symmetry is defined as the imaginary line along which an object can be folded or be divided into two identical mirror halves.

There are three lines of symmetry, namely the horizontal line of symmetry, the vertical line of symmetry, and the diagonal line of symmetry.

A circle can be divided into two identical halves by folding it along its diameter. Since a circle has infinite diameters, it has infinite lines of symmetry.


Symmetry – Definition with Examples

Shapes

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Symmetry – Definition with Examples

Angles

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Symmetry – Definition with Examples

Parallel and Perpendicular Lines

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