Quadrilateral just means “four sides”

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

## Properties

- Four sides (edges)
- Four vertices (corners)
- The interior angles add up to
**360 degrees**:

Try drawing a quadrilateral, and measure the angles. They should add to **360°**

- A polygon’s
**diagonals**are line segments from one corner to another, but not the sides.

## Types of Quadrilaterals

There are special types of quadrilateral:

Some types are also included in the definition of other types! For example a **square**, **rhombus** and **rectangle** are also ** parallelograms**.

## The Rectangle

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

## The Rhombus

A rhombus is a four-sided shape where all sides have equal length.

Also 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**.

## The Square

A square has equal sides and every angle is a right angle (90°)
Also 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). |

## The Parallelogram

A parallelogram has opposite sides parallel and equal in length. Also opposite angles are equal (angles “a” are the same, and angles “b” are the same)

*NOTE: Squares, Rectangles and Rhombuses are all Parallelograms!*