Editing Incidence structure (section)

===Nets===
A more specialized example is a {{mvar|k}}'''-net'''.  This is an incidence structure in which the lines fall into {{mvar|k}} '''parallel classes''', so that two lines in the same parallel class have no common points, but two lines in different classes have exactly one common point, and each point belongs to exactly one line from each parallel class.  An example of a {{mvar|k}}-net is the set of points of an [[affine plane]] together with {{mvar|k}} parallel classes of affine lines.