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