More Math Lessons by Cynthia Lanius Cats, canaries, or kangaroos are similar if they are alike in some way. In geometry though, similar means something very specific.
Geometric figures are similar if they have the same shape.
I don't mean two rectangles or two triangles, but really the same shape. The two rectangles are not similar. But the two rectangles below are similar. Look carefully at the last blue rectangle and you will see that it is 2 times as wide as the red rectangle and 2 times as long. Consider similarity in another way.