Quadrilateral 
Quadrilateral  

Some types of quadrilaterals



4 

{4} (for square) 

various methods; see below 

90° (for square and rectangle) 
In
The origin of the word "quadrilateral" is the two Latin words quadri, a variant of four, and latus, meaning "side".
Quadrilaterals are
The
This is a special case of the ngon interior angle sum formula (n − 2) × 180°.
All nonselfcrossing quadrilaterals
Any quadrilateral that is not selfintersecting is a simple quadrilateral.
In a convex quadrilateral, all interior angles are less than 180° and the two diagonals both lie inside the quadrilateral.
In a concave quadrilateral, one interior angle is bigger than 180° and one of the two diagonals lies outside the quadrilateral.