Similarity

Similar figures are identical in shape, but not necessarily in size.

For example, two circles are always similar:

Diagram of two circles with one bigger than the other

Two squares are always similar:

Diagram of two squares with one bigger than the other

And two rectangles could be similar:

Diagram of two rectangles with one bigger than the other

But often will not be:

Diagram of two rectangles with one longer and thinner than the other

Similar figures

Look at these similar figures:

Diagram of a combined shape with values

B is an enlargement of A. The lengths have all doubled, but notice that the angles must stay the same.

Remember that for any pair of similar figures, corresponding sides are in the same ratio and corresponding angles are equal.