Quadrilaterals

Quadrilateral just means "four sides" (quad means four, lateral means side). Any four-sided shape is a Quadrilateral. But the sides have to be straight, and it has to be 2-dimensional.

Try for Yourself

Types of Quadrilaterals

The Rectangle

		means "right angle"
	and	show equal sides

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) of a rhombus bisect each other at right angles.

The Square

		means "right angle"
		show equal sides

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

Opposite sides are parallel and equal in length, and opposite angles are equal (angles "a" are the same, and angles "b" are the same)

NOTE: Squares, Rectangles and Rhombuses are all Parallelograms!

Example: if a parallelogram has all sides equal and angles "a" and "b" are right angles, then it is also a square.

The Trapezoid (or Trapezium)

Trapezoid	Regular Trapezoid

A trapezoid (UK: trapezium) has one pair of opposite sides parallel.

It is called a regular trapezoid if the sides that aren't parallel are equal in length and both angles coming from a parallel side are equal, as shown.

A trapezoid is not a parallelogram because only one pair of sides is parallel.

The Kite

Hey, it looks like a kite. It has two pairs of sides. Each pair is made up of adjacent sides that are equal in length. The angles are equal where the pairs meet. Diagonals (dashed lines) meet at a right angle, and one of the diagonal bisects (cuts equally in half) the other.

... and that's it for the special quadrilaterals; if it doesn't fit one of those it is an Irregular Quadrilateral:

Irregular Quadrilaterals

Any quadrilateral that doesn't match one of the previous types.

Polygon

A quadrilateral is a polygon. In fact it is a 4-sided polygon, just like a triangle is a 3-sided polygon, a pentagon is a 5-sided polygom, and so on.

Play with Them

Now that you know the different types, you can play with the Interactive Quadrilaterals.

Other Names

Quadrangle ("four angles") and Tetragon ("four and polygon") are other names for Quadrilateral.