Quadrilaterals- a simple closed figure surrounded by four line segment is called a quadrilaterals. It has four sides , four angles, four vertices and two diagonals. The sum of all angles are $360^0$.
Adjacent side- having a common end point. e.g PQ & QR
Opposite side- do not have any common point. eg. PQ, RS

Similarly the adjacent angles opposite angle.
The sum of the angle of a quadrilateral is $360^0$ .

Type of quadrilaterals:
Rectangle– a quadrilateral in which opposite side are parallel & equal & each angle is $90^0$ called a rectangle.

$Area= L*B$

Square– a rectangle in which all sides are equal opposite side are, parallel and each angle is $90^0$, called a square.
$Area= side^2$

Parallelogram– a quadrilateral opposite sides are parallel & opposite angles are equal is called parallelogram.

$Area=length of one side* perpendicular height$
or $\frac{1}{2}ac*bd$ (diagonals)
$Perimiter=4* side$

Rhombus– a quadrilateral which all side are equal , opposite side are parallel and opposite angles are equal is called rhombus.
Trapezium– a quadrilateral having one opposite side is parallel is called trapezium. When if its non parallel sides are equal is called isosceles trapezium. a quadrilateral is called if their adjacent sides are equal and opposite sides are unequal.


$Area= 1/2(AB+CD)*H$
$Perimeter=Total of all sides$