A Quadrilateral has four-sides, it is 2-dimensional (a flat shape), closed (the lines join up), and has straight sides.

Characteristics of a Quadrilateral

• A quadrilateral has 4 sides, 4 angles and 4 vertices.
• A quadrilateral can be regular or irregular.
• The sum of all the interior angles of a quadrilateral is 360 degree.

Properties of Parallelogram

 There are six important properties of parallelograms to acknowledge:

• Opposite sides are congruent (AB = DC).
• Opposite angels are congruent (D = B).
• Consecutive angles are supplementary (A + D = 180°).
• If one angle is right, then all angles are right.
• The diagonals of a parallelogram bisect each other.
• Each diagonal of a parallelogram separates it into two congruent

Types of Quadrilaterals

 There are five types of quadrilaterals. The following are:

Parallelogram

A parallelogram has opposite sides parallel and equal in length. It also has opposite angles are equal.

Rectangle

 A rectangle is a four-sided shape where every angle is a right angle (90°). It also has opposite sides are parallel and of equal length.

Rhombus

 A rhombus is a four-sided shape where all sides have equal length. Its opposite sides are parallel and opposite angles are equal. Another interesting thing is that the diagonals (dashed lines in second figure) meet in the middle at a right angle. In other words they “bisect” (cut in half) each other at right angles. A rhombus is sometimes called a rhomb or a diamond.

Square

 A square has equal sides and every angle is a right angle (90°). It also has opposite sides are parallel. A square also fits the definition of a rectangle (all angles are 90°), and a rhombus (all sides are equal length).

For more details refer to ncert solutions for class 9 maths chapter 8 pdf.