You may have often heard of the term ‘symmetry’ in day to day life. Symmetry is a balanced and proportionate similarity found in two halves of an object; that is, one-half is the mirror image of the other half. In other word, a shape is said to be symmetrical if it can be divided into two identical parts. A shape which is not symmetric is referred to as asymmetrical.

Line of symmetry

An imaginary line along which a symmetrical shape can be divided to obtain identical halves is called a line of symmetry (or axis of symmetry). Every symmetrical shape has a line of symmetry. Conversely, if a shape has a line of symmetry, then it is symmetrical. For instance, a figure (or a shape) has a line of symmetry, if it can be folded so that one half of the figure coincides with the other half.

Symmetrical objects are found all around us, in nature, architecture, and art. The following figure shows some examples of symmetrical shapes. The broken line through the shape is its line of symmetry.

In geometry, a plane figure is symmetrical if it can be divided into two congruent parts. That is, the part of the figure that lies in one side of the line of symmetry is congruent to the part in the other side. If so, the shape is symmetric.