# Changes

/* Classification of Quadrilaterals */clean up & uniformity

As a consequence of the definition, the sum of the angles in a quadrilateral equals 360<sup>o</sup>, and all quadrilaterals are capable of [[tessellation|tessellating]] an [[infinite]] plane.

The [[classification]] of quadrilaterals is complex, as there are several intersecting sub-categories:

* A [[rhombus]] has four equal sides

* A [[kite]] has two pairs of adjacent equal sides

* A [[re-entrant quadrilateral]] has one internal angle greater than 180<sup>~~0~~o</sup>; this may be contrasted with a [[convex quadrilateral]] in which all internal angles are less than 180<sup>o</sup>

* An [[arrowhead]] is a re-entrant [[kite]]

* A [[square]] is both a [[rectangle]] and a [[rhombus]]

[[Category:Plane Geometry]]