# Definition, Examples, and Diagrams

What is Symmetry? – Basics | Line of Symmetry | Don’t Memorise
What is Symmetry? – Basics | Line of Symmetry | Don’t Memorise

The line of symmetry is an imaginary line that divides a shape or an object into identical halves. It is also called the axis of symmetry or the mirror line since it divides the figure symmetrically.

The diagram below shows how a line of symmetry divides a shape into identical halves that are mirror images.

Based on the orientation of the symmetry line of an object, lines of symmetry are of 3 types:

It is an imaginary vertical line that goes from top to bottom (or vice-versa) in an object and divides it into right and left mirror halves. For example, a club shape has a vertical line of symmetry.

It is an imaginary horizontal line that goes from right to left (or vice-versa) in an object and divides it into top and bottom mirror halves. For example, an arrow has a horizontal line of symmetry.

It is an imaginary diagonal or skew line that goes slanting in an object and divides it into mirror halves, as in the case of a square.

An object can have one or more lines of symmetry. Some examples involving real-life objects are:

In geometry, the number of lines of symmetry varies according to the shape as shown in case of polygons.

Find the number of lines of symmetry in the shapes given along side.

The first shape is asymmetric. So it has no lines of symmetry.
The second shape has 4 lines of symmetry.
The third shape has only 1 line of symmetry.

Ans. A rhombus has 2 lines of symmetry. They are the diagonals.

Ans. An isosceles trapezoid has 1 line of symmetry, which is the vertical line of symmetry.

Ans. An equilateral triangle has 3 lines of symmetry.

Ans. A parallelogram has no line of symmetry.

Ans. A circle has infinite number of symmetry.