Quadrilateral: Polygon with four sides

Sometimes, the term quadrangle is used (similar to the term "triangle"), while other times, the term tetragon is used (similar to pentagon, 5-sided polygon, and hexagon, 6-sided polygon). A quadrilateral with vertices ${\displaystyle A}$, ${\displaystyle B}$, ${\displaystyle C}$, ${\displaystyle D}$ is sometimes written as ${\displaystyle \square ABCD}$.

Quadrilateral
Some types of quadrilaterals
Edges and vertices	4
Schläfli symbol	{4} (for square)
Area	various methods, usually base time height
Internal angle (degrees)	90° (for square and rectangle)

The origin of the word quadrilateral is the two Latin words quadri, a variant of four, and latus, meaning "side".

Quadrilaterals can be either complex, also called crossed (self-intersecting), or simple (not self-intersecting). Simple quadrilaterals are either convex or concave.

All the sides of a quadrilateral are straight, and the interior angles of a quadrilateral add up to 360°.

${\displaystyle \angle A+\angle B+\angle C+\angle D=360^{\circ }.}$

This is a special case of the n-gon interior angle sum formula: (n − 2) × 180°.

All non-self-crossing quadrilaterals tile the plane, by repeated rotation around the midpoints of their edges.

There are 6 special kinds of quadrilaterals; square, rectangle, rhombus, parallelogram, kite, and trapezoid. Technically, squares, rectangles, and rhombuses are types of parallelograms.

• Cube
• Cuboid