Editing Discrete geometry (section)

===Structural rigidity and flexibility===
{{main|Structural rigidity}}
[[File:Structural rigidity basic examples.svg|thumb|150px|Graphs are drawn as rods connected by rotating hinges. The [[cycle graph]] C<sub>4</sub> drawn as a square can be tilted over by the blue force into a parallelogram, so it is a flexible graph. K<sub>3</sub>, drawn as a triangle, cannot be altered by any force that is applied to it, so it is a rigid graph.]]

'''Structural rigidity''' is a [[combinatorics|combinatorial theory]] for predicting the flexibility of ensembles formed by [[rigid body|rigid bodies]] connected by flexible [[Linkage (mechanical)|linkage]]s or [[hinge]]s.

Topics in this area include:
*[[Cauchy's theorem (geometry)|Cauchy's theorem]]
*[[Flexible polyhedron|Flexible polyhedra]]