 Edges an vertices4
Schläfli seembol{4} (for square)
Aurievarious methods;
Internal angle (degrees)90° (for square an rectangle)

In Euclidean plane geometry, a quadrilateral is a polygon wi fower sides (or edges) an fower vertices or corners. Sometimes, the term quadrangle is uised, bi analogy wi triangle, an sometimes tetragon for consistency wi pentagon (5-sidit), hexagon (6-sidit) an so on.

The origin o the wird "quadrilateral" is the twa Laitin wirds quadri, a variant o fower, an latus, meanin "side."

Quadrilaterals are simple (nae self-intersectin) or complex (self-intersectin), an aa cried crossed. Simple quadrilaterals are either convex or concave.

The interior angles o a simple (an planar) quadrilateral ABCD add up tae 360 degrees o arc, that is

$\angle A+\angle B+\angle C+\angle D=360^{\circ }.$ This is a special case o the n-gon interior angle sum formula (n − 2) × 180°. In a crossed quadrilateral, the fower interior angles on either side o the crossin add up tae 720°.

Aw convex quadrilaterals tile the plane bi repeatit rotation aroond the midpynts o thair edges.