Pronunciation: /ˈreɪ di əl ˈsɪm ɪ tri/ Explain

 Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now) Manipulative 1: Radial symmetry of a five pointed star. Click on the blue point in the manipulative and drag it to change the figure.

A geometric object has radial symmetry if it has congruent parts radiating out from a central point. The five-pointed star in figure 1 has radial symmetry. Each of the points is identical to the other points. All of the points extend out the same way from the central point. Another way to think of radial symmetry, involves rotating the object around the central point. If the object is rotated by any angle other than a full circle and lies exactly on top of the preimage, then the object has radial symmetry.

Objects that are radially symmetric can differ on how many points of symmetry they have. The star in figure 1 has 5 point radial symmetry. In nature, there are many plants and animals that have 3 point, 5 point, 6 point and 8 point symmetry. Some of these are shown in the table below.

### Radial Symmetry in Nature

IllustrationDescription
This apple was cut in two across the middle. Notice the five seeds radiating out from the middle.
Most sea stars have 5 point symmetry. This one has 11 point symmetry.
Sea anemones have radial symmetry.
A chicory flower has radial symmetry. The different levels of petals each have radial symmetry and are offset from each other.
Table 1: Radial symmetry in nature. Click on the images to see a larger version.

McAdams, David E. Radial Symmetry. 5/5/2011. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/r/radialsymmetry.html.

### Image Credits

All Math Words Encyclopedia is a service of Life is a Story Problem LLC.