The line of symmetry is the imaginary line that divides something into two exactly equal and opposite parts. These two parts mirror each other; you can fold the figure in half and the two parts match exactly.
Take a look at a monarch butterfly.
Notice how the wings are identical but opposite; they are an example of bilateral symmetry. Other animals also have bilateral symmetry — humans, dogs, cats, elephants.
Some animals have what is called radial symmetry — body parts arranged around a center point. Instead of being mirror images on only one line, animals with radial symmetry are mirror images wherever you draw a line across the body — jellyfish, starfish, sea anemones.
To learn more about butterfly symmetry, print off the FREE download by clicking on the photo below. Finish each butterfly so that one half matches the other, making them symmetrical.