i want some important points about understanding the quadrilaterals

InEuclidean plane geometry, aquadrilateralis apolygonwith fouredges(or sides) and fourverticesor corners. Sometimes, the termquadrangleis used, by analogy withtriangle, and sometimestetragonfor consistency withpentagon(5-sided) andhexagon(6-sided), or4-gonfor consistency withk-gons for arbitrary values ofk.

The word "quadrilateral" is derived from the Latin wordsquadri, a variant of four, andlatus, meaning "side".

Quadrilaterals aresimple(not self-intersecting) orcomplex(self-intersecting), also called crossed. Simple quadrilaterals are eitherconvexorconcave.

Theinterior anglesof a simple (and planar) quadrilateralABCDadd up to 360degrees of arc, that is

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

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

All non-self-crossing quadrilateralstile the planeby repeated rotation around the midpoints of their edges.