Illustrated · 1 min
Similar shapes have the same shape but aren't necessarily the same size
If two shapes are similar, it means that they share the exact same shape, but don't have to be the same size. In other words, all their angles share the same measure and are in the same order, but their sides may be longer (though they share the same proportion). Location and rotation don't matter at all for similarity.
All the blue shapes in the image below are similar to one another. The red shape is not similar to any of the blue shapes. Because shapes ABC and GIH have sides that are the same length as well as angles that share the same measure, they are congruent.