A quadrilateral is a polygon that has four angles, four sides, and four vertices. The word ‘quadrilateral’ is derived from the Latin words ‘Quadri’, which means four, and 'latus' which means side.

The above image is an example of a quadrilateral.

**Parts of a quadrilateral:**

- Angles: ∠A, ∠B, ∠C, and ∠D
- Sides: AB, BC, CD, and DA
- Vertices: 4 vertices-A, B, C, D
- Diagonals: AC and BD are diagonals

**Properties of a quadrilateral:**

Some properties are common to all quadrilaterals. They are:

- They have four vertices.
- They have four sides.
- The sum of all interior angles is 360°.
- They have two diagonals.

**Properties of a square:**

- All sides of the square are equal in length.
- All the sides are parallel to each other.
- The interior angles of a square are 90°. It means the sides are right-angled.
- The diagonals are perpendicular bisectors.

**Properties of a rectangle:**

- The opposite sides are of the same length.
- All the sides are parallel to each other.
- The interior angles of a rectangle are 90°. It means the sides are right-angled.
- The diagonals are perpendicular bisectors.

**Properties of a parallelogram:**

- The opposite sides are of the same length.
- The opposite sides are parallel to each other.
- The diagonals bisect each other.
- The opposite angles measure the same.
- The adjacent angles add up to 180°.

Properties of a rhombus:

- The four sides are equal in length.
- The opposite sides are always parallel to each other.
- The opposite angles measure the same.
- The diagonals are perpendicular bisectors.
- The adjacent angles add up to 180°.

Properties of a trapezium:

- Only one pair of opposite sides are parallel to each other.
- The diagonals bisect each other in the same ratio.
- The adjacent sides are supplementary. That means they add up to 180°.

Properties of a kite:

- A pair of adjacent sides are of the same length.
- Only one pair of opposite angles measure the same.
- The largest diagonal bisects the smallest diagonal.

Non-examples of quadrilaterals: Quadrilaterals that do not have four sides and four angles are called non-examples of quadrilaterals.

The above images are the non-examples of quadrilaterals.

**Real-life examples of quadrilaterals:**

There are many real-life examples of quadrilaterals. For example, a book, a tabletop, a door, a picture frame, etc.

- Number Systems
- Algebra
- Co-ordinate Geometry
- Geometry
- Mensuration
- Statistics And Probability
- Polynomials
- Linear Equations in Two variables
- Statistics
- Probability
- Introduction to Euclids Geometry
- Lines and Angles
- Triangles
- Areas of Parallelograms and Triangles
- Circles
- Herons Formula
- Constructions
- Surface Area and Volumes