Called <a href="https://en.wikipedia.org/wiki/Regular_polygon" class="extiw" title="w:Regular polygon">regular</a> dodecagons, a few <a href="https://en.wiktionary.org/wiki/polygon#Noun" class="extiw" title="wiktionary:polygon">polygons</a> have twelve <a href="https://en.wiktionary.org/wiki/side#Noun" class="extiw" title="wiktionary:side">sides</a> within the image.  Consider two regular <a href="https://en.wiktionary.org/wiki/dodecagon#Noun" class="extiw" title="wiktionary:dodecagon">dodecagons</a> sharing <a href="https://en.wiktionary.org/wiki/center#Noun" class="extiw" title="wiktionary:center">their center</a> and all <a href="https://en.wiktionary.org/wiki/vertices#Noun" class="extiw" title="wiktionary:vertices">their vertices.</a>  If they are different, one of them <a href="https://en.wikipedia.org/wiki/Convex_set" class="extiw" title="w:Convex set">is convex</a>, the other <a href="https://en.wikipedia.org/wiki/Regular_polygon#Regular_star_polygons" class="extiw" title="w:Regular polygon">is stellated.</a>  A side of any of them is <a href="https://en.wiktionary.org/wiki/diagonal#Noun" class="extiw" title="wiktionary:diagonal">a diagonal</a> of the other.
<a href="//commons.wikimedia.org/wiki/User:Baelde" title="User:Baelde">Baelde</a>
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