Symmetry
Symmetry describes how the congruent parts of a shape are related to each other. To see what this means, let's examine a couple of geoboard figures.
Here's a different kind of symmetry:
It's possible for a shape to have more than one line of reflection - here's an example:
The second shape we looked at has order 4 rotational symmetry (also called quarter-turn symmetry) because it can fit into its 'frame', or outline, four ways. The figure above has order 2 rotational symmetry (also called half-turn symmetry) because it can only fit into its 'frame' two ways. If a shape must rotate 360 degrees to fit back into its outline, then we say it has no rotational symmetry.
Shapes can have all kinds of combinations of reflectional and rotational symmetry. Can you imagine or sketch shapes that has these kinds of symmetries?