When two or more parts of an object or shape are identical after a flip, slide or turn (rotation), then the shape has symmetry.
Symmetry is a quality of being made up of exactly similar parts facing each other or around an axis.
What is Line of Symmetry
The imaginary line or axis along which you fold the figure to obtain the symmetrical halves is called the line of symmetry. It basically divides an object into mirror-image halves
Note – The line of symmetry can be vertical, horizontal or diagonal
One line of symmetry. – Figure is symmetrical only about one line. This line of symmetry can be horizontal, vertical or diagonal.
Two line of symmetry. – Figure is symmetrical only about 2 line. These lines of symmetry can be horizontal or vertical.
Note – Some figures have more than two lines of symmetry
In the following figures, you can see there are multiple lines of symmetry which can cut the figure to form mirror image
Symmetry of a circle
In a circle (all the lines passing through the center are lines of symmetry)
Asymmetry or Asymmetrical objects/shapes – objects or shapes which have no any line of symmetry are asymmetrical objects or shapes. Asymmetry is lack of symmetry
Types of Symmetry
a. Reflection symmetry – When one side of the object is the mirror image of the part on the other side, when the line of symmetry is drawn, then called reflection symmetry.
b. Rotational Symmetry – Rotational symmetry (or radial symmetry) is when an object is rotated in a certain direction around a point.
In above example the figure is rotated by 90o, hence, they are also called 90o rotational symmetry.
c. Point Symmetry – A figure has point symmetry if there is a central point so that the part of the figure on one side of the central point is the reflection of the part on the other side
Note – 180o rotational symmetry is also a point symmetry
d. Translational Symmetry – If the object is moved from one position to another, the same orientation in the forward and backward motion is called translational symmetry.
In other words, it is defined as the sliding of an object about an axis.
Real life examples of symmetry