A <a href="https://en.wikipedia.org/wiki/complete_quadrangle" class="extiw" title="en:complete quadrangle">complete quadrangle</a> (left) and a complete quadrilateral (right).
<a href="https://en.wikipedia.org/wiki/User:David_Eppstein" class="extiw" title="wikipedia:User:David Eppstein">David Eppstein</a> at <a href="https://en.wikipedia.org/wiki/" class="extiw" title="wikipedia:">English Wikipedia</a>
Transferred from <span class="plainlinks"><a class="external text" href="https://en.wikipedia.org">en.wikipedia</a></span> to Commons.