What are congruent and similar shapes?

  • Two identical 2D shapes are said to be congruent.

  • Two 2D shapes that share the same proportions are similar.

  • The angles and side lengths can help us decide which type they are.

A short video explaining the concept of congruent and similar shapes.

How do we determine the type of shape?

Congruent

If one shape can be rotated, reflected or translated to fit exactly onto another shape, then the shapes are said to be congruent. Congruent shapes have the same area, size, angles and lengths as each other.

Similar

If we enlarge one shape to make it bigger or smaller, then the shapes are said to be similar. The corresponding sides of similar shapes must be in the same proportion and the corresponding angles are identical. Similar shapes are not the same size as each other.

Some examples of similar shapes are: different size circles, an A4 and an A5 piece of paper.