Update and add index

html/complexity.html

@@ -53,6 +53,8 @@ Chaos</a> - The transition zone between order and disorder.</li>
 The whole is greater than the sum of the parts.</li>
 <li><a href="https://en.wikipedia.org/wiki/Fractal">Fractal</a> -
 Self-similar structure.</li>
+<li><a href="https://en.wikipedia.org/wiki/Hysteresis">Hysteresis</a> -
+Dependence of the state of a system on its history.</li>
 <li><a href="https://en.wikipedia.org/wiki/Holon_(philosophy)">Holon</a>
 - System that is both a whole and a part.</li>
 <li><a